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CONCRETE 
INSPECTION 


NET  BOOK  —  This  Book  is  supplied 
to  the  trade  on  terms  which  do  not 
admit  of  discount. 

THE  MYRON  C.  GLARK  PUBLISHING  CO. 


Associate  Editor  Engineering-Contracting;  Author  of 

The  Chicago  Main    Drainage   Channel;  joint 

Author  with  A.  W.  Buel   of  "Reinforced 

Concrete  ";  Joint  Author  with  Halbert 

P.  Gillette  of  "Concrete  Construc- 

Hon—Methods  and  Cost."  ^fgJ&^^-Xl  ^ 

^^  OF  THE 

UNIVERSOS 

OF 

CHICAGO  AND  NEW  YORK 

The  Myron  C.  Clark  Publishing  Co. 


LONDON 

B.  &  F.  N,  §pon,  Ltd.,  57  Haymarket 
1909 


CONCRETE 
INSPECTION 


A  MANUAL   OF  INFORMATION   AND 

INSTRUCTIONS  FOR  INSPEC- 

TORS    OF 

CONCRETE  WORK 

WITH 
STANDARD  AND  TYPICAL  SPECIFICATIONS 


BY 

CHARLES   S.   HILL,   C.   E. 

¡ 

Associate  Editor  Engineering-Contracting;  Author  of 

The  Chicago  Main    Drainage   Channel;  joint 

Author  with  A.  W.  Buel   of  "Reinforced 

Concrete  ";  Joint  Author  with  Halbert 

P.  Gillette  of  "Concrete  Construc- 

tion — Methods  and  Cost."  j^f^^^"^-^<% 

^  OF  THE 

UNIVERSITY 

OF 

ÍMlifor]^ 

CHICAGO  AND  NEW  YORK 

The  Myron  C.  Clark  Publishing  Co. 


LONDON 

£..  &  F.  N,  §pon,  Ltd.,  57  Haymarket 
1909 


Copyright  1909 

By 

The  Myron  C.  Clark  Publishing  Co. 


OF  THE 

UNIVERSITY 

OF 


PREFACE. 

Careful  inspection   is  a  vital  factor   in 
securing   safe     and     enduring     concrete 
work.     No  matter  how  well  the  engineer 
may   design,   his     work     will     come     to 
naught    unless    his    design    is    accurately 
carried  out  by  careful  and  skillful  work- 
manship  with  good  materials.     The  con- 
struction  must  be  good  and  assurance  of 
good    construction    is    liad    in    conscien- 
tious    and    competent    inspection    alone. 
The    duties    of    concrete    inspection    are 
various  and  numerous.     It  is  the  purpose 
of    this    volume    to    give    a    schedule    of 
these   duties   and   such  general   and   spe- 
cific    instructions    as    are    necessary    to 
insure    their      performance.      The      book 
consists   of  a   series   of  rules   and   direc- 
tions  to   be  followed   in   inspecting  con- 
crete   work    with    brief    explanations    of 
the   reasons   for   each    rule    and    of   their 
importance.      It    is    believed    that    every- 
thing  said  is  based  on  sound  practice  and 
acknowledged    authority,    and    that    the 
young   inspector   will   not   be   led   astray, 
even  if  the  oíd  experienced  inspector  is 
taught  nothing  that  he  does  not  already 
know.     Where   it   is   possible   to   say  so 
much,    it    is    not    easy    to    tell    when    to 
stop   or  when  one  has  stopped  short  of 
saying  all  he  should,  and  the  author  will 


194261 


not  be  surprised  to  find  that  he  has  erred 
at  times  in  both  respects.  If  those  of  his 
readers  who  discover  such  errors  will 
tell  him  of  them,  the  author  will  see  that 
they  are  corrected.  By  working  to- 
gether  in  this  manner  it  will  be  possi- 
ble  to  produce  a  manual  which  will  be 
of  increasing  influence  toward  good  in- 
spection  in  concrete  work,  and  this  is  the 
solé   purpose   of   the   author's   work. 

C    S    H 
August  15,  1909. 


TABLE    OF    CONTENTS. 

Page 

CHAPTER    I.— INSPECTION     OF     CON- 
CRETE  MATERIALS    1 

Cement:  Tested  Cement — Mili  Tested 
Cement — Field  Tested  Cement— Untest- 
ed  Cement— Reject  Cement — Storage  of 
Cement.  Sand:  Specifications  for  Sand 
— Determinations  for  Sand — Shape  of 
Grains— Size  of  Grains— Mineral  Com- 
position — Cleanliness — Voids.  Aggre- 

gates:  Specifications  for  Aggregates— 
Determinations  for  Aggregate.  Water: 
Puré  Water — Clean  Water — Quantity  of 
Water. 

CHAPTER    II.— INSPECTION    OF    PRO- 

PORTIONING    AND    MIXING 17 

Proportioning:  Method  of  Measuring — 
Standard  Units  of  Measure — Verifica- 
tion  of  Measures — Accurate  Measuring 
— Sizes  of  Batches.  Mixing:  Methods 
of  Hand  Mixing — Specifications  for 
Hand  Mixing — Mixing  Boards — Size  of 
Batch  in  Hand  Mixing — System  in  Hand 
Mixing  Operations — Hand  Mixing  for 
Reinforced  Concrete — Concrete  Mixing 
Machinery — Type  of  Mixer — Charging 
Batch  Mixers — Charging  Continuous 
Mixers — Number  of  Turns — Discharging 
with  a  Drop — Cleaning   the  Mixer. 

CHAPTER  III.— INSPECTION  OF  FORM 

WORK   26 

Construction  of  Forms — Alignment  of 
Forms — Strength  of  Forms — Rigidity  of 
Forms — Loads  on  Forms — Wetting  of 
Forms — Oiling  Forms — Cleaning  Forms 
— Removing  Forms  for  Finishing — Lum- 
ber  for  Forms — Quality  of  Lumber — 
Size  and  Finish  of  Lumber — Cleaning 
Form  Lumber — Fabrication  of  Forms — 
Tight  Joints — Beveling  Strips  and  Mold- 
ings — Spacing  and  Squaring  Column 
Molds — Cleaning  Column  Molds — Cam- 
ber  of  Beam  Forms — Wire  Ties  and 
Spacers — Projecting  Ends  of  Wire  Wall 
Ties — Bolt  Ties  and  Spacers — Anchoring 
Pyramidal  or  Batter  Forms — Arch  Cen- 
ters — Forms  for  Arch  Sections — Molds 
for       Ornaments — Time     of      Removing 


vi  CONTENTS 


Page 
Forms — Method  of  Removing  Forms — 
Removing  Column  Forms — Removing 
Beam  Forms — Striking  Centers — Swell- 
ing  of  Forms — Bracing  of  Forms — Loca- 
tion  of  Shores— Length  of  Shores — 
Square  Ends  on  Shores — Wedges — 
Footings  for  Shores — Caps  for  Shores — 
Time  of  Removing  Shores — Method  of 
Removing   Shores — Runways. 

CHAPTER  IV.— INSPECTION  OF  REIN- 

FORCEMENT     42 

Checking,  Assorting  and  Storing  Steel 
— Assembling  of  Reinforcement — Num- 
ber  of  Bars — Sizes  of  Bars — Form  of 
Bars — Spacing  of  Bars — Cleanliness  of 
Steel— Bending  of  Bars — Splicing  of 
Bars — Protruding  Ends  of  Bars — Fas- 
tening  Reinforcement — Wiring  Rein- 
forcement— Placing  Column  Reinforce- 
ment— Spacing  Column  Bars — Tying 
Column  Bars — Splicing  Column  Bars — 
Placing  of  Beam  Reinforcement — Plac- 
ing Wall  Reinforcement — Placing  Con- 
duit  Reinforcement — Placing  Reinforce- 
ment for  Circular  Tanks. 

CHAPTER    V.— INSPECTION    OF    CON- 

CRETING     50 

Depositing  in  Buckets— Depositing 
Through  Chutes — Method  of  Pouring — 
Time  of  Pouring — Tamping  Dry  and 
Médium  Concrete — Puddling  Wet  Con- 
crete— Pouring  Slabs — Pouring  Beams — 
Pouring  T-Beams — Pouring  Columns — 
Puddling  Columns — Places  for  Stopping 
Concrete  —  Stopping  Slabs  —  Stopping 
Beams  and  Girders — Stopping  Columns 
— Stopping  Walls — Joining  New  Con- 
crete to  Oíd — Concreting  Connections — 
Coping  Construction— Filling  Bolt  Holes 
— Cutting  Finished  Concrete — Concreting 
Arches — Concreting  in  Transverse  Sec- 
tions — Concreting  in  Longitudinal  Sec- 
tions — Filling  Over  Arches — Drainage — 
Expansión  Joints — Wetting  Finished 
Work — Depositing  Concrete  Under  Wa- 
ter— Depositing  Through  Tremie — De- 
positing in  Bags — Detecting  Wash — 
Protection  from  Currents — Rubble  Con- 
crete— Concreting  in  Freezing  Weather: 
Adding  Substances  to  Mixing  Water — 
Salt  in  Mixing  Water — Calcium  Chloride 
in  Mixing  Water — Heating  Concrete 
Materials — Frozen  Lumps  in  Concrete 
—  Covering      the      Concrete  —  Artificial 


CONTENTS  vii 


Page 
Heaters — Finishing  Surfaces:  Spaded 
Finish — Spaded  and  Troweled  Finish — 
Mortar  Face  Finish — Dry  Concrete  Fac- 
ing — Grout  Washes — Tooling  Concrete 
— Scrubbed  Finish — Acid  Wash  Finish — 
Gravel  or  Pebble  Finish — Plaster  Fin- 
ish—Painting    Concrete    Surfaces. 

CHAPTER  VI.— INSPECTION   OF  SIDE- 

WALK  CONSTRUCTION    73 

Preparation  of  Foundation — Material 
for  Sub-Base — Compacting  Sub-Base — 
Wetting  Sub-Base — Material  for  Forms 
— Alignment  and  Level  of  Forms — Stak- 
ing  of  Forms — Spacing  of  Forms — Mix- 
ing — Size  of  Batch  Mixed — Placing  Base 
Concrete — Tamping  Base — Preserving 
Joints  in  Base — Expansión  Joints — 
Method  of  Placing  Top  Mortar — Con- 
sistency  of  Top  Mortar — Time  of  Plac- 
ing Top  Mortar — Bonding  Top  Mortar 
to  Hardened  Base — Marking  Wearing 
Coat — Finishing  Edges  of  Walk — Pro- 
tection  from  Frost — Protection  from 
Rain — Protection  from  Sun — Fractional 
Slabs. 

CHAPTER  VII.  —  INSPECTION  OF 
MOLDING  AND  DRIVING  CON- 
CRETE   PILES    81 

Driving  Piles  in  Place — Constructing 
Piles  in  Place — Reinforcing  Piles  in 
Place— Cast  Piles— Molds  for  Cast  Piles 
— Reinforcing  Cast  Piles — Casting  Piles 
in  Tiers — Concreting  Cast  Piles — Driv- 
ing  Cast   Piles — Handling   Cast   Piles. 

CHAPTER       VIII.  —  INSPECTION       OF 

CAST    CONCRETE    WORK 84 

Methods  of  Molding — Mixing  for  Dry 
Mixture  Blocks — Consistency  of  Dry 
Mixtures  —  Size  of  Dry  Mix- 
ture Batches — Molds  for  Dry  Mix- 
ture Blocks — Tamping  Dry  Mixtures — 
Facing  Dry  Mixture  Blocks — Removing 
Dry  Mixture  Blocks  from  Molds — Stack- 
ing  Dry  Mixture  Blocks — Protecting  Dry 
Mixture  Blocks — Sprinkling  Dry  Mix- 
ture Blocks — Removing  Dry  Molded 
Blocks  from  Platens — Curing  Period  for 
Dry  Mixture  Blocks — Puddling  Wet 
Mixtures — Removing  Molds  from  Wet 
Mixture  Blocks — Provisión  for  Handling 
Molded  Blocks — Accuracy  of  Shape 
and   Dimensions. 


viii  CONTENTS 


Page 
CHAPTER  IX.— STANDARD  AND  TYPI- 

CAL    SPECIFICATIONS    90 

Specifications  for  Cement — Specifica- 
tions  for  Portland  Cement  Concrete 
and  Reinforced  Concrete — Specifications 
for  Building  Construction,  St.  Louis 
Code — Proposed  Standard  Building 
Regulations  for  the  Use  of  Reinforced 
Concrete  —  Specifications  for  Aren 
Bridge  Construction — Specifications  for 
Sidewalks — Specifications  for  Hollow 
Building  Blocks. 


CHAPTERI.  INSPECTIONOF  CON- 
CRETE MATERIALS. 
The  materials  used  must  be  of  good 
quality  if  a  good  quality  of  concrete 
work  is  to  be  obtained.  The  materials 
for  making  concrete  are  hydraulic  ce- 
ment,  sand,  a  coarse  aggregate  like 
crushed  stone  or  gravel  and  water.  If 
the  quality  of  any  one  or  more  of  these 
materials  is  poor,  an  inferior  concrete  is 
produced.  They  must  all  be  inspected 
for  quality,  and  the  cement  at  least 
should  be  carefully  tested  for  quality. 

CEMENT. 

The  commercial  unit  of  measurement 
of  concrete  is  the  barrel;  the  unit  of 
shipment  is  the  bag.  A  barrel  of  Port- 
land  cement  contains  380  lbs.  of  cement, 
and  the  barrel  itself  weighs  20  lbs.;  there 
are  four  bags  (cloth  or  paper  sacks)  of 
cement  to  the  barrel  and  the  regulation 
cloth  sack  weighs  W2  lbs.  The  amount 
of  cement  in  a  barrel  varíes,  due  to  dif- 
ferences  in  weight  of  cement  and  to 
differences  in  compacting  the  cement 
into  the  barrel.  A  light  burned  Portland 
cement  weighs  100  lbs.  per  struck 
bushel;  a  heavy  burned  Portland  cement 
weighs  118  to  125  lbs.  per  struck  bushel. 
The    number    of    cubic    feet    of    packed 

1 


2  CONCRETE    1NSPECTI0N. 

Portland  cement  in  a  barrel  ranges  from 

3  to  31/&.  Natural  cements  are  lighter 
than  Portland  cements.  A  barrel  of 
Louisville,  Akron,  Utica  or  other  west- 
ern  natural  cement  contains  265  lbs.  of 
cement  and  weighs  15  lbs.  itself;  a  bar- 
rel of  Rosendale  or  other  eastern  ce- 
ment contains  300  lbs.  and  the  barrel  it- 
self weighs  20  lbs.  There  are  3%  cu.  ft.  in 
a  barrel  of  Louisville  cement.  Usually 
there  are  three  bags  to  a  barrel  of  nat- 
ural cement.  When  cement  is  emptied 
and  shoveled  into  boxes  (loóse  cement) 
it  measures  from  20  to  30  per  cent  more 
than  when  packed  in  the  barréis.  When 
loóse,  dry  Portland  cement  is  wetted  it 
shrinks  about  15  per  cent  in  volume.  The 
amount  of  cement  paste  produced  by  a 
barrel  of  Portland  cement  ranges  from 
3.2  to  3.8  cu.  ft.  The  amount  of  cement 
in  a  cubic  yard  of  concrete  varíes  with 
the  voids  in  the  sand  (see  sand)  and 
in  the  aggregates  (see  aggregates)  and 
with  the  proportions  of  the  mixture;  the 
following  rule  will  give  the  approximate 
amount: 

Add  together  the  number  of  parís  of 
cement,  sand  and  aggregate  and  divide 
this  sum  into  ten,  the  quotient  will  be 
approximately  the  number  of  barréis  of 
cement  per  cubic  yard* 

♦Concrete  Construction  —  Methods  and 
Costs,"  Gillette  and  Hill. 


1NSPECTI0N    OF    MATERIALS.  3 

Cement  is  generally  shipped  in  car- 
load  lots  (100  to  150  bbls.)  and  the  usual 
practice  is  to  test  a  sample  from  each 
shipment  or  carload. 

Tested  Cement. — Tested  cement  is  re- 
quired  for  practically  all  concrete  vvork 
— it  is  the  duty  of  the  inspector  to  make 
certain  that  only  tested  cement  is  used 
in  the  work. 

Mili  Tested  Cement. — When  cement  is 
tested  at  the  mili,  be  on  guard:  (1)  For 
substitutions  in  transit.  (2)  For  deteri- 
oration  in  transit.* 

(1)  To  guard  against  substitution,  the 
cement  should  be  loaded  for  shipment 
at  the  mili  under  the  eye  of  the  mili  in- 
spector and  the  car  sealed  by  him  or 
the  shipment  otherwise  marked  by  him 
in  such  a  manner  that  any  tampering 
with  the  individual  packages  or  with 
the  shipment  as  a  whole  can  be  detected. 
Notice  of  each  shipment  and  a  record 
of  all  identifying  data  should  be  for- 
warded  to  the  field  inspector.     The  field 

*The  conditions  surrounding  cement  dar- 
ing  transportaron  may  readily  be  of  such 
ai  nature  as  to  alter  its  physical  properties 
completely — so  that  the  material  received 
in  the  field  is  radically  different  from  that 
tested  at  the  mili.  Some  engineers  object  to 
mili  tested  cement  for  this  among  other  rea- 
sons.  The  matter  concerns  the  field  inspec- 
tor only  in  the  respect  that  it  emphasizes  the 
necessity  of  extra  watchfulness  to  make 
sure,  in  so  far  as  inspection  is  able,  that  the 
cement  has  not  suffered  in  the  interval  be- 
tween  the  mili  test  and  the  receipt  of  the 
material  in  the  field. 


4  CONCRETE    INSPECTION. 

inspector  should  make  certain  that  the 
shipment  as  received  corresponds  in 
every  particular  with  the  description  fur- 
nished  by  mili  inspector. 

(2)  *To  guard  against  deterioration 
make  sure  that  the  packages  are  re- 
ceived unbroken  and  dry,  that  the  cem- 
ent  is  of  good  appearance,  and  that  it  is 
free  from  injurious  lumpiness.  Oíd  well 
seasoned  cement  is  frequently  lumpy, 
but  the  lumps  can  be  easily  crushed  and 
powdered  in  the  fingers.  If  the  lumps 
can  be  crushed  by  the  fingers  only  with 
diflíiculty  the  presumption  is  that  wet- 
ting  has  occurred  and  partial  setting 
taken  place.  Such  cement  should  be  re- 
jected  or  held  for  field  tests. 

Field  Tested  Cement. — The  preferred 
practice  of  engineers  is  to  test  the  cem- 
ent   after    it    has    been    received    in    the 


♦Sometimes  cement  has  to  be  stored  for 
long  periods  of  time,  say  over  winter,  in 
sheds  with  thin  walls.  The  pressure  in  high 
piles  sometimes  makes  the  bags  hard  and 
very  often  it  is  thought  to  have  partly  set. 
If  the  hardening  is  due  to  pressure  the  bags 
should  be  carried  into  the  sun  and  turned 
over  rather  roughly  every  half  hour  for  three 
or  four  hours.  Then  turn  it  over  about  a 
dozen  times  and  put  through  a  29  mesh 
screen.  This  screen  should  be  a  rectangular 
shaking  screen  and  the  cement  should  be 
run  into  the  sacks  on  scales  and  weighed  to 
get  the  required  weight.  The  lumps  re- 
tained  on  the  screen  should  be  thrown  away 
and  not  be  crushed.  They  should  not  be 
mashed  so  as  to  go  through  the  screen.  The 
cost  of  this  handling  is  seldom  over  3  cts.  per 
bag — including  the  cost  of  the  cement 
thrown  away. 


INSPECTION    OF    MATERIALS.  5 

field.  The  duty  of  the  field  inspector  is 
to  see  that  no  cement  is  used  in  the 
work  until  it  has  been  tested  and  ac- 
cepted  by  the  field  testing  laboratory. 
To  this  end  the  packages  should  be  so 
stacked  and  marked  for  identification 
(see  Storage  of  Cement)  (1)  that  the 
untested  material  is  separated  and  easily 
distinguishable  from  the  tested  material, 
(2)  that  each  shipment,  which  is  the  sub- 
ject  of  a  sepárate  test,  is  separated  and 
easily  distinguishable  from  the  other 
shipments.  The  field  inspector  should 
receive  notice  from  the  testing  labora- 
tory of  the  "acceptance"  or  "rejection" 
of  each  shipment  and  that  shipment 
should  be  marked  to  correspond.  He 
should  allow  no  cement  to  be  taken  from 
storage  onto  the  work  until  it  has  been 
"accepted"  by  the  testing  laboratory. 
"Rejected"  cement  should  be  removed 
from  the  field.  (See  Rejected  Cement.) 
Untested  Cement. — The  use  of  untest- 
ed cement  depends  wholly  on  the  repu- 
tation  of  the  manufacturer  (the  brand) 
for  reliability.  It  is  not  good  practice. 
The  inspector,  when  untested  cement  is 
used,  can  do  little  more  than  make  cer- 
tain  that  the  cement  is  so  stored  as  to 
be  protected  from  injury  and  be  watch- 
ful  for  substitution.  There  is  little  dan- 
ger  of  cement  being  wrongly  branded 
when  it  is  bought  direct  from  the  manu- 


6  CONCRETE    1NSPECTI0N. 

facturers,  but  dealers  sometimes  sell  in- 
ferior cement  in  bags  having  the  brand 
mark  and  ñame  of  well  known,  reliable 
cements.  Comparison  of  the  cement  re- 
ceived  with  cement  known  to  be  of  the 
brand  purchased,  to  see  that  it  corre- 
sponds  in  color,  texture  and  general  ap- 
pearance  and  that  it  behaves  similarly  in 
the  work,  will  often  detect  such  substi- 
tution.  The  inspector  cannot  do  much 
more  than  this  without  making  tests. 
Shipment  by  the  manufacturer  of  infe- 
rior quality  cement  can  be  guarded 
against  only  by  tests. 

Rejected  Cement. — Rejected  cement 
should  be  removed  from  storage  at  once 
under  the  eye  of  the  inspector,  and  some 
or  all  of  the  packages  marked  with  a 
prívate  mark  so  that  it  can  be  recognized 
if  attempt  is  made  to  ship  it  back  again. 

Storage  of  Cement. — The  requisites 
for  proper  storage  of  cement  are  protec- 
tion  from  dampness  and  excessive  heat, 
and  ventilation  with  plenty  of  dry  air. 
The  storage  house  should  have  a  floor 
raised  from  the  ground  and  be  thorough- 
ly  rain  and  snow  proof.  The  cement 
should  be  so  stored  that  sepárate  ship- 
ments  are  separated  and  easily  accessi- 
ble  for  marking,  inspection  and  removal. 
(See  Field  Tested  Cement.)  An  ideal 
arrangement  is  to  divide  the  house  into 
bins,  each  holding  a  car  load   shipment 


INSPECTION    OF    MATERIALS.  7 

(100  to  150  bbls.);  over  each  bin  fasten  a 
placard  giving:  (a)  the  brand;  (b)  the 
number  of  packages;  (c)  the  ñame  and 
number  of  the  car;  (d)  the  date  re- 
ceived;  (e)  a  space  for  the  mark  "ac- 
cepted"  or  "rejected,"  with  date.  What- 
ever  the  arrangement  selected  by  the 
contractor  may  be,  the  inspector  should 
insist  upon  a  thoroughly  damp-proof 
structure  and  upon  the  shipments  being 
so  stacked  that  each  is  accessible  for  in- 
spection,  marking  and  removal.  Storage 
of  cement  in  the  open  should  be  limited 
to  small  quantities  to  be  used  immedi- 
ately  in  the  work.  The  bags  should  not 
be  piled  on  wet  ground,  but  on  plank- 
ing,  sidewalk,  pavement,  etc.,  and  they 
should  be  stacked  in  compact  piles 
which  can  be  covered  with  tarpaulin  in 
case  of  showers.  The  inspector  should 
see  that  tarpaulins-  are  provided  and  are 
ready  for  immediate  use. 

SAND. 

Sand  constitutes  from  one-third  to 
one-half  of  the  volume  of  concrete.  Sand 
composed  of  round  grains  makes  quite 
as  strong  mortar  as  does  sand  composed 
of  angular  or  sharp  grains.  Sand  con- 
taining  up  to  at  least  10  per  cent  evenly 
distributed  fine  mineral  matter,  such  as 
clay,  is  not  objectionable.  Sand  com- 
posed of  a  mixture  of  fine  and  coarse 
grains  is  the  best;  as  between  a  coarse 


8  CONCRETE    INSPECTION. 

and  a  fine  sand  of  one  size  of  grains,  the 
coarse  sand  is  the  better.  Sand  contain- 
ing  mica  should  be  rejected.  Natural 
sand  is  employed  for  the  majority  of 
concrete  work.  Practically  the  only  sub- 
stitute  for  natural  sand  that  is  much 
used  is  pulverized  stone,  either  the  dust 
and  fine  screenings  produced  in  crush- 
ing  rock  or  an  artificial  sand  made  by 
reducing  suitable  rocks  to  powder.  The 
technology  of  sand  for  mortars  is  quite 
complex  and  the  inspector  desiring  a 
more  complete  knowledge  should  study 
the  standard  treatises  on  concrete.  Sand 
plays  an  important  role  in  the  strength 
and  durability  of  concretes,  and  its  in- 
spection  allows  of  neither  neglect  ñor 
carelessness. 

Specifications  for  Sand. — Specifications 
for  sand  commonly  stipulate  its  nature, 
whether  natural  or  artificial;  the  mineral 
composition;  the  shape  and  size  of  the 
grains;  the  allowable  contení  of  loam, 
clay  or  other  foreign  matter,  and  the 
allowable  percentage  of  voids.  Engi- 
neers  differ  in  their  requirements  and 
the  inspector  must  be  bound  by  the 
specifications;  his  duty  is  to  determine 
whether  the  sand  employed  meets  the 
requirements  of  the  specifications  and  to 
see  that  only  sand  of  the  specified  quali- 
ty  and  character  is  used. 

Determinations  for   Sand. — The   usual 


'  INSPECTION    OF    MATERIALS.  9 

determinations  for  sand  are:  Shape  of 
grains,  size  of  grains,  mineral  composi- 
tion  of  grains,  cleanliness  and  amount  of 
voids.  These  determinations  elaborated 
and  enlarged  by  specific  gravity  tests 
and  strength  tests  of  mortars  con- 
stitute  the  usual  laboratory  investiga- 
tions  of  sand.  Frequently  all  sand  de- 
terminations are  made  in  the  works'  lab- 
oratory and  the  inspector  has  only  to  see 
that  none  but  approved  sand  is  used, 
but  the  inspector  should  be  prepared  to 
make  at  least  approximate  determina- 
tions. The  following  methods  can  be 
employed: 

Shape  of  Grains. — Determination  of 
the  shape  of  the  sand  grains  is  best 
made  by  examining  them  through  a 
magnifying  glass.  A  pinch  of  the  sand 
rubbed  between  the  thumb  and  finger 
will  by  its  "feel"  tell  whether  the  grains 
are  sharp  or  rounded. 

Size  of  Grains. — Determine  the  size  of 
grains  by  sieving  the  sand.  For  com- 
plete analysis  the  following  sizes  of 
sieves  are  recommended  by  Mr.  W.  B. 
Fuller:  Nos.  10,  15,  20,  30,  40,  60,  74, 
100,  150,  and  200.  Fewer  sieves  will 
serve  all  the  ordinary  demands  of  field 
inspection;  a  No.  5,  No.  15  and  a  No.  50 
will  give  as  complete  an  analysis  as  is 
ordinarily  necessary. 

Mineral    Composition.  —  The    mineral 


10  CONCRETE    INSPECTION. 

composition  of  sand  can  be  determined 
accurately  only  by  laboratory  analysis. 
A  sufficiently  cióse  determination  for  or- 
dinary  purposes  can,  however,  be  made 
by  visual  examination  aided  by  a  mag- 
nifying  glass,  by  one  reasonably  familiar 
with  the  different  rocks.  The  glassy 
look  of  quartzite  forming  the  bulk  of  the 
grains  of  silicious  sands  is  familiar  to  all. 
The  visual  determination  of  feldspar  and 
basalt  is  almost  as  easy,  and  mica  is  fa- 
miliar in  appearance  to  every  one. 

Cleanliness. — Cleanliness  can  be  deter- 
mined with  suíncient  accuracy  by  elu- 
triation  as  follows:  Place  a  weighed 
quantity  of  sand  in  a  glass  beaker,  add 
clean  water,  and  stir  vigorously;  allow  to 
settle  for  15  seconds  and  decant  off  the 
water  into  a  vessel;  repeat  the  process 
until  the  water  pours  off  clear;  evapórate 
the  water  that  has  been  decanted  off  and 
weigh  the  residue;  divide  the  weight  of 
the  residue  by  the  total  weight  of  the 
sand  put  into  the  beaker  and  the  result 
will  be  the  percentage  of  impurities.  A 
less  exact  method,  but  one  that  will 
suffice  in  many  instances,  is  to  agítate  a 
sample  of  sand  with  water  in  a  test  tube 
or  an  even  size  glass  vessel  or  bottle  and 
allow  the  solid  matter  to  settle;  the 
sand  will  settle  first  and  on  top  of  it  the 
fine  dirt  and  the  relative  proportions  of 
the  two  can  be  estimated  by  observing 
their  relative  depths. 


INSPECTION    OF    MATERIALS.  11 

Voids. — Determinaron  of  voids  can  be 
made  in  the  following  ways:  (1)  Fill  a 
1,000  c.  c.  cylinder  with  sand  and  weigh 
it;  divide  net  weight  of  sand  in  grains  by 
1,000  c.  c.,  or  the  volume,  to  get  the  net 
weight  per  c.  c.;  divide  this  by  specific 
gravity  of  sand  (2.65)  and  multiply  by 
100  to  get  percentage  of  solid  content; 
subtract  per  cent  of  solid  content  from 
100  to  get  percentage  of  voids.*  (2) 
Calcúlate   by  the   following  equatiomf 

S  —  Sp 

Percentage   of  voids=(l )100. 

R 
in  which 
5==Net  weight  of  a  cubic  foot  of  sand. 
/>=Percentage  of  moisture. 
i^Weight  of  cubic  foot  of  solid  rock  from 
accompanying  table. 

Weight 
Specific  of  cu.ft. 

Material.  gravity.  of  solid  rock. 

Sand    2.65  165 

Gravel     2.66  165 

Conglomérate    2.6  162 

Granite    2.7  168 

Limestone     2.6  162 

Trap    2.9  180 

Slate    2.7  168 

Sandstone    2.4  150 

Cinders    (bituminous)1.5  95 

Note:  To  find  p,  dry  10  lbs.  of  sand 
at  even  temperature  of  at  least  212°  F., 
until  there  is  no  further  loss  of  weight. 
Subtract  weight  of  dried  sand  from  orig- 
inal weight   (10  lbs.)   and  divide  remain- 

♦"Practical  Cement  Testing,"  W.  P.  Tay- 
lor. 

f'Concrete  Plain  and  Reinforeed,"  Taylor 
and    Thompson. 


12  CONCRETE    INSPECTION. 

der  by  original  weight  (10  lbs.)  to  get 
percentage  of  moisture  or  p. 

Neither  of  the  preceding  methods  is 
much  more  intricate  or  tedious  than  the 
method  of  filling  a  measure  of  sand  with 
water  and  both  are  much  more  accurate. 

In  any  method  of  determining  voids 
care  should  be  taken  to  fill  the  sand  into 
the  measure  always  in  the  same  manner; 
that  is,  always  loóse  or  always  shaken, 
since  the  void  space  is  affected  by  the 
manner  of  filling. 

AGGREGATES. 

The  aggregates  commonly  used  in 
making  concrete  are  crushed  or  broken 
stone,  gravel,  clay  and  cinders.  Slag 
and  cinders  are  used  chiefly  for  fire 
proof  building  work;  being  the  producís 
of  combustión  they  are  supposed  to 
make  a  specially  fire-resisting  concrete. 
Stone  produced  by  crushing  any  of  the 
harder  and  tougher  varieties  of  rock  is 
suitable  for  concrete.  Perhaps  the  best 
stone  is  produced  by  crushing  trap  rock. 
Crushed  trap  besides  being  hard  and 
tough  is  angular  and  has  an  excellent 
fracture  surface  for  holding  cement;  it 
also  withstands  heat  better  than  most 
stone.  Next  to  trap  the  hard,  tough 
crystalline  limestones  make  perhaps  the 
best  all  around  concrete  aggregate;  cem- 
ent adheres  to  limestone  better  than  to 
other    rocks.      Limestone,    however,    cal- 


INSPECTION    OF    MATERIALS.  13 

cines  when  subjected  to  fire,  and  is, 
therefore,  objected  to  by  many  engineers 
for  building  construction.  The  harder 
and  denser  mica-schists,  granites  and 
syanites  make  good  stone  for  concrete. 
Gravel  makes  one  of  the  best  possible 
aggregates  for  concrete.  The  conditions 
under  which  gravel  is  produced  by  na- 
ture  make  it  reasonably  certain  that  only 
the  harder  and  tougher  rocks  enter  into 
its  composition.  The  rounded  shape  of 
the  component  particles  permits  gravel 
to  be  more  closely  compacted  than  brok- 
en  stone;  the  mixture  is  also  generally  a 
fairly  well  balanced  composition  of  fine 
and  coarse  particles.  The  surfaces  of 
the  particles  being  generally  smooth 
give  perhaps  a  poorer  bond  with  the  cem- 
ent  than  most  broken  stone.  In  the 
matter  of  strength  recent  tests  show 
that  there  is  very  little  choice  between 
gravel  and  broken  stone  concrete.  Cin- 
ders  for  concrete  should  be  steam  cin- 
ders  free  from  unburned  coal  and  soot, 
and  are  best  when  screened  from  fine 
ash.  Slag  for  concrete  is  blast  furnace 
slag  broken  to  proper  size.  It  should  be 
free  from  sulphur;  a  slag  some  months 
oíd  is  preferable,  as  aeration  has  had 
opportunity  to  remove  the  sulphur. 

Specifications  for  Aggregates. — Speci- 
fications  for  aggregates  usually  stipulate 
the  kind,  the  mineral  nature  of  the  par- 


14  CONCRETE    1NSPECT10N. 

ticles,  the  size  and  shape  of  the  partióles, 
the  cleanliness,  the  amount  of  voids  and 
whether  or  not  it  shall  be  screened. 
Specifications  vary  in  their  requirements 
and  the  inspector  must  be  bound  by  the 
particular  specification  under  which  the 
work  is  being  done.  His  duty  is  to  de- 
termine that  the  aggregate  used  meets 
the  requirements  of  the  specification  and 
to  make  certain  that  no  other  aggregate 
is  used  in  the  work. 

Determinations  for  Aggregate. — The 
usual  determinations  for  aggregates  are: 
Shape  of  particles,  size  of  particles,  min- 
eral composition  of  particles,  cleanliness 
and  amount  of  voids. 

Methods. — Any  of  the  methods  used 
in  making  determinations  for  sand  can 
be  used  in  making  determinations  for 
aggregates.  As  a  matter  of  fact,  visual 
examination  is  usually  all  that  is  neces- 
sary  for  any  of  the  determinations  ex- 
cept  that  for  voids  and  for  exact  analysis 
of  the  various  sizes  of  particles  com- 
posing  the  aggregate.  Voids  can  be  de- 
termined  with  fair  accuracy  by  filling  a 
measure  of  aggregate  with  water;  owing 
to  the  larger  particles  the  error  due  to 
entrapped  air  is  small.  The  other  meth- 
ods as  described  for  sand  are,  however, 
nearly  as  simple. 

WATER. 

Reasonably  clean  and  puré   sea  water 


1NSPECT10N    OF    MATERIALS.  15 

or  fresh  water  are  both  suitable  for  con- 
crete. 

Puré  Water. — If  any  doubt  exists  as 
to  the  purity  of  the  available  water  it 
should  be  analyzed  or  given  a  practical 
test.  Water  which  contains  salts  in  so- 
lution  in  small  quantities  is  suitable  for 
concrete,  but  strongly  acid  or  strongly 
alkaline  water  is  doubtful  and  may  be 
dangerous.  Water  from  streams  into 
which  manufacturing  wastes  are  dis- 
charged,  bog  water  and  water  in  alkali 
country  are  always  open  to  doubt. 
Brackish  sea  water  or  sea  water  from 
harbors  receiving  sewage  and  industrial 
wastes  is  also  open  to  doubt.  The  in- 
spector should  ascertain  and  report  these 
facts  to  the  engineer. 

Clean  Water. — Water  carrying  in  sus- 
pensión considerable  quantities  of  min- 
eral or  vegetable  matter  is  objectionable, 
as  is  also  water  containing  sewage 
sludge.  The  inspector  should,  in  lack  of 
specified  directions,  report  such  facts  to 
the  engineer. 

Quantity  of  Water. — The  quantity  of 
water  required  for  concrete  varies  with 
the  consistency  of  the  concrete  specified 
and  this  may  vary  from  an  earth  damp 
mixture  to  one  that  is  a  veritable  slop 
The  proper  amount  of  water  is  that 
amount  which  will  produce  a  mixture  of 
the  specified  consistency — the  consisten- 


16  CONCRETE    1NSPECTI0N. 

cy  of  the  mixture  should  be  watched  and 
not  the  dose  of  water.  For  wet  con- 
crete, such  as  is  now  most  commonly 
employed,  the  amount  of  water  can  be 
calculated  by  the  following  rule: 

Multiply  the  parts  of  sand  by  8,  add  24 
to  the  product,  and  divide  the  total  by  the 
sum  of  the  parts  of  sand  and  cement. 

This  gives  the  per  cent  by  weight  of 
water  required.  When  "soupy"  concrete 
is  specified,  the  soupy  consisteney  of 
thick  broth  is  meant. 


^     OF   THE 

UNIVERSíTY 

OF 


CHAPTER       II.     INSPECTION      OF 

PROPORTIONING  AND  MIXING. 

PROPORTIONING. 

American  engineers  proportion  concrete 
mixtures  by  measure,  thus  a  1-2-4  concrete 
is  one  composed  of  1  volume  of  cement,  2 
volumes  of  sand,  and  4  volumes  of  aggre- 
gate.  The  duty  of  the  inspector  is  to 
make  certain  that  the  specified  proportions 
are  accurately  and  uniformly  adhered  to. 
This  is  simply  a  task  of  accurate  meas- 
uring — it  requires  (1)  that  definite  meas- 
uring  units  be  employed ;  (2)  that  the  ac- 
curacy  of  the  measuring  boxes,  hoppers, 
etc.,  be  verified ;  (3)  that  the  filling  of  the 
measuring  boxes,  hoppers,  etc.,  be  exact, 
and  (4)  that,  when  two  or  more  box  or 
hopperfuls,  etc.,  go  to  make  up  a  batch, 
the  exact  number  is  employed  for  each  and 
every  batch.  The  inspector  should  bear  in 
mind  that  while  splitting  hairs  is  not  war- 
ranted  by  the  exactness  of  the  process  of 
concrete  making  as  it  is  conducted  in  prac- 
tical  construction  work,  slipshod  and  care- 
less  methods  and  practices  should  not  be 
tolerated. 

Method  of  Measuring. — When  the  meth- 
od  of  measuring  is  not  stipulated  in  the 
specifications,  it  is  tacitly  understood  that 
it  shall  correspond  to  accepted  practice  in 

17 


18  CONCRETE    INSPECTION. 

respect  to  accuracy,  etc.  Beyond  this  qual- 
ification  the  contractor's  choice  is  unre- 
stricted.  The  inspector  shall  see  that  a 
method  is  adopted  whose  accuracy  can  be 
readily  verified  and  which  is  sufficiently 
simple  for  the  ordinary  workman  to  carry 
out  without  likelihood  of  frequent  error. 

Standard  Units  of  Measure. — Determine 
the  units  of  measure  at  the  beginning.  If 
they  are  not  stated  in  the  specifications  see 
that  a  definite  understanding  is  had  by 
both  engineer  and  contractor  of  what  they 
shall  be.  Cement  is  different  in  volume 
when  measured  loóse  and  when  packed  in 
the  barrel ;  cement  barréis  vary  in  volume  of 
contents.  It  should  be  definitely  under- 
stood  by  engineer,  contractor  and  inspec- 
tor: (1)  Whether  the  volume  of  cement 
used  is  its  volume  measured  loóse  or  its 
volume  as  packed  in  the  barrel;  (2)  what 
the  cubic  contents  of  a  barrel  of  cement,  or 
a  bag  of  cement,  shall  be  called.*  If  the 
stone  is  measured  in  empty  cement  barréis 
have  it  understood  whether  a  barrelful  is 


♦The  contractors'  unit  of  measurement  of 
cement  is  the  bag.  Contractors  universally 
count  one  bag  as  being  equal  to  1  cu.  ft.  and 
many  engineers  specify  this  figure.  It  is  the 
most  convenient  unit  of  measure  in  actual 
construction  work  and  for  this  reason  and 
because  of  contractors'  practice,  the  author 
would  urge  its  adoption  as  standard  prac- 
tice. The  following  is  a  clause  covering  this 
point  taken  from  the  specifications  for  con- 
crete  of  Mr.    Ernest   McCullough: 

"The  unit  of  measurement  for  cement  shall 
be  the  bag  as  received  from  the  manufac- 
turer  having  a  gross  weight  of  not  less  than 
95  lbs.     Such  a  packed  bag  shall  be  consid- 


PROPORTIONING    AND    MIXING.  19 

the  volume  measured  with  the  heads 
knocked  out  or  the  volume  contained  be- 
tween  heads ;  there  is  %  cu.  ft.  difference. 
If  the  sand  and  stone  are  measured  in 
wheelbarrows  have  it  definitely  understood 
what  the  volume  of  a  wheelbarrow  load 
shall  be  called ;  there  is  a  cubic  foot  differ- 
ence between  the  capacity  of  a  wheelbar- 
row, water  measure,  and  the  load  usually 
carried  by  men  in  wheeling. 

Verification  of  Measures. — The  meas- 
ures  used  should  be  verified  to  make  sure 
that  each  holds  the  amount  intended.  This 
can  be  very  simply  done  by  using  a  known 
measure  to  fill  the  measuring  box,  etc., 
employed,  or  the  volume  of  the  box,  etc., 
can  be  computed  mathematically. 

Accurate  Measuring. — See  that  the  filling 
of  the  measures  is  reasonably  exact,  and, 
when  several  measures  of  each  material 
are  required  to  make  up  a  batch,  that  the 
exact  number  is  adhered  to.  When  the 
men  are  being  rushed  or  have  grown  care- 

ered  as  being-  equal  to  one  cubic  foot  of  ce- 
ment.  The  contractor  shall  mix  his  concrete 
in  batches  calling  for  even  bags  wjien  possi- 
ble.  If  compelled  to  use  fractions  of  bags 
said  fractions  shall  be  weighed  upon  the  as- 
sumption  that  the  neat  cement  weighs  not 
less  than  94  lbs.  per  cubic  foot.  If  bags  re- 
ceived  from  the  manufacturer  contain  less 
than  94  lbs.  net  of  cement  the  contractor 
shall  bring  up  the  weight  with  additional  ce- 
ment. If  the  bags  weigh  uniformly  more 
than  is  here  called  for  the  contractor  shall 
be  allowed  to  remove  the  excess  cement  pro- 
vided  each  bag  thus  altered  is  altered  by 
weight.  The  inspector  shall  weigh  one  bag 
in  forty  as  the  cement  is  received,  in  order 
to  check  weights." 


20  CONCRETE    INSPECT10N. 

less  through  lack  of  watching,  they  are 
very  likely  to  partly  fill  or  to  overfill  the 
measures ;  this  is  especially  Hable  when 
filling  buckets,  hoppers  or  cars  to  mark 
by  means  of  chutes  from  overhead  bins, 
also  when  the  measuring  is  being  done  by 
wheelbarrow  loads.  Skipping  a  measure- 
ful  when  several  measurefuls  are  required 
to  make  up  a  batch  is  another  common 
error.  Lack  of  system  is  chiefly  responsi- 
ble  for  this  error.  The  operations  of 
measuring  should  follow  a  regular  routine 
or  sequence  which  should  not  be  varied 
from  and  a  double  check  system  should  be 
used  by  which  both  the  cement  man  and 
the  mixer  operator  check  the  number  of 
measures.  While  skipping  a  measureful  of 
sand  or  aggregate  entails  no  dangerous 
consequences  (a  batch  of  extra  rich  con- 
crete results  simply)  the  skipping  of  a 
measureful  of  cement  results  in  a  weak 
spot  in  the  work.  In  reinforced  concrete 
building  work  it  results  in  a  weak  girder 
or  column  and  is  dangerous.  No  chances 
which  vigilance  and  caution  can  avoid 
should  be  taken  in  measuring  and  charg- 
ing  the  cement  contení  of  concrete  for  re- 
inforced concrete  work.  Only  a  man  of 
intelligence  should  measure  and  feed  the 
cement  and  he  should  be  made  to  under- 
stand  that  safety  to  life  and  property  de- 
pends  on  the  accuracy  of  his  work. 

Automatic  Measuring  Devices. — When 
automatic   measuring   devices  are   used  to 


PR0P0RT10NING    AND    MIXING.  21 

proportion  the  concrete  see :  (1)  That 
they  are  regulated  to  give  the  proper  pro- 
portions,  (2)  that  the  materials  do  not 
clog,  choke  or  arch  in  the  feed  hoppers ; 
(3)  that  the  feed  hoppers  are  kept  amply 
supplied  with  materials. 

Sizes  of  Batches. — See  that  the  batches 
are  of  such  size  that  they  can  be  propor- 
tioned  without  using  fractions  of  meas- 
ures.  If  the  batch  calis  for  parts  of  bags 
or  barréis  of  cement  or  parts  of  barrows 
of  sand  or  stone  the  proper  división  is 
hard  to  get  from  workmen  in  the  rush  of 
work. 

MIXING. 

Concrete  is  mixed  by  (1)  hand  turnim/ 
with  shovels  and  hoes,  (2)  by  concrete 
mixing  machines.  Mixing  by  hand  usually 
is  employed  only  where  the  amount  of  con- 
crete to  be  mixed  is  small  or  where  fre- 
quent  moves  of  the  place  of  mixing  are 
necessitated  as  in  sidewalk  work.  The 
increasing  portability  of  mixing  machines 
is  doing  away  rapidly  with  the  last  named 
reason  for  hand  work.  Except  for  isolated 
small  jobs  the  use  of  mixing  machines  is 
general  practice. 

Methods  of  Hand  Mixing. — One  of  the 

following  two  general  methods  is  usually 
employed  in  mixing  concrete  by  hand:  (1) 
The  materials  are  spread  in  layers  one  on 
top   of   the   other   and    turned     dry     with 


22  CONCRETE    INSPECTION. 

shovels ;  after  being  dry  mixed  water  is 
added  to  the  mixture  and  the  mass  is  again 
turned  with  shovels.  (2)  The  cement  and 
sand  are  mixed  into  a  wet  mortar,  to 
which  the  stone  is  added,  and  the  whole 
mass  is  incorporated  by  turning  with 
shovels.  The  number  of  turnings,  the 
order  of  the  various  operations  and  other 
details  of  both  methods  vary  with  the  prac- 
tice  of  the  individual  engineer. 

Specifications  for  Hand  Mixing. — See 
that  the  specifications  are  clear  as  to  the 
method  of  doing  hand  mixing  and  as  to 
the  perfection  of  the  results  required. 
Specifications  are  most  likely  to  be  am- 
biguous  concerning  the  number  of  turns 
required  and  as  to  what  constitutes  a  turn. 
The  inspector  should  make  his  mind  clear 
on  these  points  and  should  see  that  the 
understanding  between  engineer  and  con- 
tractor is  definite.  In  case  the  specifica- 
tions do  not  stipulate  the  methods  of  mix- 
ing, etc.,  see  that  it  is  definitely  understood 
by  engineer,  contractor  and  inspector  what 
methods  and  results  will  be  accepted  as 
satisfactory. 

Mixing  Boards. — See  that  a  suitable 
platform  is  provided  on  which  to  do  the 
mixing  and  that  it  is  kept  clean  from  ad- 
hering  material  and  from  foreign  matter. 
See  that  the  planking  is  tight  enough  to 
prevent  material  leakage  of  water  carrying 
cement.     See   that   the    platform    is    large 


PROPORTIONING    AND    MIXING.  23 

enough  to  admit  of  efficient  and  rapid  mix- 
ing. 
Size   of  Batch  in  Hand  Mixing. — See 

that  the  quantity  of  concrete  in  each  batch 
is  no  greater  than  the  quantity  that,  under 
the  conditions,  can  be  mixed  and  depos- 
ited  in  permanent  position  in  the  work  be- 
fore  the  cement  begins  to  set. 

System  in  Hand  Mixing  Operations. — 
See  that  the  mixing  operations  are  con- 
ducted  according  to  a  regular  system. 
This  permits  the  inspector  to  check  the 
work  and  tends  to  produce  uniformity  of 
product  that  decreases  the  necessity  of 
constant  inspection  for  and  correction  of 
faults  in  the  mixture. 

Hand  Mixing  for  Reinforced  Concrete. 

— See  that  hand  mixing  for  reinforced 
concrete  work  is  done  deliberately  and 
carefully.  Hand  mixing  should  be  avoid- 
ed  for  reinforced  concrete  work  if  possi- 
ble,  but  if  allowed  in  an  emergency,  the 
inspection  should  be  rigid.  Hand  mixing 
as  done  for  ordinary  mass  concrete  work 
will  not  do  for  reinforced  concrete  work. 

Concrete  Mixing  Machinery. — Concrete 
mixers  are  of  two  types :  (1)  batch  mixers 
in  which  the  materials  are  charged,  mixed 
and  discharged  in  batch  units,  (2)  contin- 
uous  mixers  in  which  the  materials  are 
charged,  mixed  and  discharged  in  a  con- 
¿inuous  stream.  A  third  división  is  some- 
times   made   into  gravity     mixers;     some 


24  CONCRETE    1NSPECTI0N. 

gravity  mixers  are  batch  mixers  and  some 
are  continuous  mixers.  General  practice 
favors  batch  mixers  for  reinforced  con- 
crete work  and  wherever  a  specially  uni- 
form,  well  mixed  concrete  is  required. 
Continuous  mixers  are  considered  satisfac- 
tory  for  mass  concrete  work,  foundations, 
etc. 

Type  of  Mixer. — See  that  the  mixer  used 
is  of  an  approved  type  and  that  it  is  erect- 
ed  and  operated  in  such  a  manner  that  the 
charging,  mixing,  discharging  and  regula- 
tion  of  the  materials  is  uniform,  efficient 
and  certain. 

Charging  Batch  Mixers. — See  that  the 
batch  is  composed  of  the  proper  propor- 
tions  and  that  it  is  so  charged  into  the 
mixer  that  the  principie  of  batch  unit  mix- 
ing is  fulfilled.  This  means  that  all  the 
batch  must  be  in  the  mixer  and  held  there 
as  a  unit  throughout  at  least  the  mínimum 
number  of  turns  or  other  operations  neces- 
sary  to  produce  a  mixture  of  the  required 
perfection. 

Charging  Continuous  Mixers. — See  that 
the  materials  are  fed  evenly  into  the  mixer 
in  the  proper  proportions.  If  the  mixer 
has  automatic  measuring  attachment  see 
that  the  various  feed  hoppers  are  kept 
amply  full  and  that  the  material  does  not 
"bridge"  or  "choke"  and  so  cease  to  feed 
into  the  mixer  drum.  If  the  mixer  is  fed 
by  shoveling  see  that  the  shoveling  is  done 


PROPORTIONING    AND    MIXING.  25 

from  properly  proportioned  piles  of  cement, 
sand  and  aggregate,  that  each  shovelful 
contains  a  proper  mixture  of  materials, 
and  that  the  shoveling  is  done  at  a  uni- 
form  rate.  Even  feeding  is  essential  to 
good  results  from  a  continnous  mixer  and 
the  inspector  should  watch  this  operation 
carefully. 

Number  of  Turns. — See  that  the  mixer 
is  given  the  requisite  number  of  turns  for 
each  batch.  A  certain  number  of  turns 
is  required  to  produce  a  concrete  of  any 
standard  perfection  of  mix,  if  less  than 
this  number  of  turns  is  given  to  the  batch 
an  inferior  concrete  results.  The  requisite 
number  of  turns  can  readily  be  determined 
by  trial  mixing  of  a  few  batches  and  when 
once  determined  that  number  should  be  set 
as  the  mínimum  allowable. 

Discharging  with  a  Drop. — See  that  the 
concrete,  in  discharging  the  mixer,  does 
not  drop  or  fall  for  any  considerable  dis- 
tance.  Such  a  free  fall  has  a  tendency  to 
segregate  the  stone  from  the  mortar. 

Cleaning  the  Mixer. — See  that  the  mixer 
is  cleaned  of  all  adhering  mortar  or  con- 
crete when  work  is  discontinued  at  night 
or  for  other  reasons.  A  mixer  caked  with 
cement  operates  with  reduced  efficiency 
and  in  addition  the  caked  cement  is  Hable 
to  break  or  jar  loóse  in  large  pieces  and  be 
discharged  with  the  fresh  concrete  in 
which  jt  forrns  a  dangerous  body. 


CHAPTER  III.  INSPECTION  OF 
FORM    WORK. 

Forms  are  the  molds  in  which  the  con- 
crete is  shaped  to  its  purpose.  They  are 
constructed  of  wood  or  of  steel;  wood 
forms  are  most  used.  The  cost  of  forms 
is  a  very  large  item  in  the  cost  of  most 
kinds  of  concrete  work;  the  contractor 
should,  therefore,  be  assisted  in  every  legit- 
ímate effort  to  make  the  greatest  possible 
use  of  his  forms.  Safety  must  always 
come  first,  however ;  a  great  many  concrete 
building  failures  have  been  chargeable  to 
unwise  handling  of  forms,  particularly  to 
the  removal  of  fon.xS  before  the  concrete 
was  hard  and  strong  enough  to  carry  its 
loads  unsupported.  The  inspector  should 
watch  with  care  all  portions  of  formwork 
having  any  bearing  on  safety.  Forms  being 
the  molds  in  which  the  concrete  is  shaped, 
any  error  in  dimensions  or  alignment 
means  a  corresponding  error  in  the  mold- 
ed  concrete  member.  The  inspector  should 
also  make  certain  that  the  forms  are  per- 
fect  for  their  purpose  in  these  respects.  It 
should  be  accepted  as  a  cardinal  principie 
in  form  inspection  that :  The  accuracy  of 
no  detall  shall  be  taken  for  granted;  it 
must  be  veriñed. 

Construction  of  Forms. — See  that  the 
construction  of  forms  is  such  that  they  can 

26 


INSPECTION    OF    FORM    WORK.  27 

be  removed  without  injury  to  the  concrete, 
and  that  they  can  be  erected  accurately. 
Construction  which  necessitates  the  use  of 
heavy  crow-bars  or  hand  sledging  to  take 
the  forms  apart  is  dangerous  to  the  con- 
crete. The  best  form  construction  is  one 
in  which  the  parts  are  assembled  by  means 
of  clamps  and  wedges,  and  not  by  nails. 

Alignment  of  Forms. — See  that  all  forms 
are  erected  in  exact  alignment,  both  ver- 
tically  and  horizontally ;  that  column  and 
wall  forms  are  plumb ;  that  girder  boxes 
and  wall  forms  are  without  winds  or 
twists ;  that  slab  centers  are  level,  etc.  If  the 
forms  stand  any  considerable  time  between 
erection  and  time  of  depositing  the  con- 
crete, check  the  alignment  just  be  f  ore 
placing  the  concrete.  Check  the  alignment 
after  storms  and  high  winds.  Keep  care- 
ful  check  on  the  alignment  of  movable 
panel  forms  used  in  wall  construction ;  they 
require  especial  skill  and  care  to  keep  in 
line.  Watch  the  alignment  during  the 
placing  of  the  concrete ;  the  loading  may 
distort  the   forms. 

Strength  of  Forms. — See  that  all  forms 
have  ampie  strength  to  support  properly 
the  loads  they  are  called  upon  to  carry. 
Proper  support  of  concrete  in  construction 
work  means  immovable  support,  not  merely 
support  sufficient  to  prevent  collapse. 

Rigidity  of  Forms. — See  that  the  forms 
are  rigid,  immovable  under  the  loads  they 
have  to  carry. 


28  CONCRETE    1NSPECT10N. 

Loads  on  Forms. — See  that  the  loads  011 
forms  are  restricted  to  those  for  which 
the  forms  are  designed.  These  comprise 
the  weight  of  the  concrete  and  such  neces- 
sary  construction  loads  as  the  weight  of 
workmen,  runways,  wheelbarrows,  etc. 
Storage  on  the  forms  of  construction 
materials  for  future  use  should  be  pro- 
hibited. 

Wetting  of  Forms. — See  that  all  forms, 
if  not  coated  with  some  oil,  are  thor- 
oughly  wetted  on  both  sides  before  con- 
crete is  poured.  A  soaking  wetting  is 
necessary;  see  that  the  water  is  thoroughly 
applied  to  the  boards  until  they  will  take 
up  no  more  moisture.  Even  when  the 
inside  of  the  forms  is  oiled  it  is  a  good 
plan,  especially  on  hot  days,  to  wet  down 
the  outside  of  the  forms  thoroughly. 

Oiling  Forms. — See  that  the  forms  are 
oiled  at  each  setting,  just  before  depositing 
the  concrete.  Take  care  that  an  excess  of 
oil  or  other  unguent  is  not  used;  take  care 
that  spots  from  which  adhering  concrete 
has  been  cleaned  are  especially  well  oiled, 
concrete  shows  a  tendency  to  stick  again 
to  the  places  on  which  it  has  once  stuck. 
Never  grease  or  oil  forms  where  concrete 
is  to  be  plastered  or  whitewashed ;  the 
grease  will  discolor  the  work  and  make  the 
bond  between  coating  and  wall  concrete 
poor. 

Cleaning  Forms. — See  that  all  forms 
(beam  boxes,   column   molds,   wall   forms, 


INSPECTION    OF    FORM    WORK.  29 

etc.)  are  carefully  and  thoroughly  cleaned 
from  shavings,  chips,  sawdust  and  adhering 
or  accumulated  foreign  matters  of  all  kinds 
before  concrete  is  allowed  to  be  deposited. 
The  cleaning  should  be  done  just  previous 
to  placing  the  concrete. 

Removing  Forms  for  Finishing. — Where 
the  surface  is  to  be  finished  by  scrubbing 
or  other  process  requiring  the  concrete  to 
be  still  green,  see  that  proper  provisión  is 
made,  in  the  construction  of  the  forms,  for 
laying  bare  the  concrete  as  fast  as  it 
rcaches  the  required  hardness. 

Lumber  for  Forms. — See  that  the  lumber 
for  forms  is  of  such  quality,  size  and 
finish  that  it  promises  absolute  stability  and 
reasonably  perfect  work  under  the  condi- 
tions.  It  is  the  contractor's  right,  if  unre- 
stricted  by  the  specifications,  to  use  such 
lumber  as  he  pleases,  providing  he  gives 
the  results  required,  but  it  is  the  inspector's 
right  to  insist  that  the  lumber  used  prom- 
ises the  specified  results  with  reasonable 
certainty. 

Quality  of  Lumber. — Lumber  from  weak 
and  treacherous  woods,*  that  is  cross- 
grained,  that  contains  knots,  wind-shakes, 
or  rot  which  endanger  its  safety  under  the 
conditions,  should  not  be  allowed.  See 
that  the  lumber  is  not  so  dry  that  when 
soaked  by  the  concrete  it  will  swell  so  as 


*White  pine,  yellow  pine,  spruce,  Oregon 
pine  and  redwood  are  suitable  for  forms; 
hemloek  is  unreliable. 


30  CONCRETE    INSPECTION. 

to  bulge  and  distort  the  forms ;  see  that  the 
lumber  is  not  so  green  that  it  will  shrink 
so  as  to  leave  open  joints. 

Size  and  Finish  of  Lumber. — See  that 
the  size  of  the  lumber  is  such  that  it  will 
not  deflect,  bulge  or  warp  unduly  under 
the  conditions.  See  that  it  is  straight  and 
true  and  of  even  thickness.  See  that  the 
finish  is  such  as  will  give  the  surface  re- 
sults  desired. 

Cleaning  Form  Lumber. — See  that  form 
lumber  which  has  been  previously  used  is 
thoroughly  cleaned  of  adhering  concrete  or 
dirt.  The  cleaning  should  be  done  bcfore 
the  lumber  is  again  built  into  forms. 

Fabrication  of  Forms. — See  that  the  car- 
pentry  is  workmanlike,  the  measures  accu- 
rate,  the  lines  true  and  square,  the  joints 
cióse,  and  the  finish  neat.  Form  work  is 
not  cabinet-makers'  work,  but  it  is  good 
all  around  carpenters'*  work,  and  it  should 
be  done  in  a  workmanlike  manner.  Watch 
particularly  the  piecing  out  of  beam  boxes, 
the  alteration  of  column  molds,  etc. 

Tight  Joints. — See  that  all  joints  in  forms 
are  fairly  tight.  Absolute  water  tightness 
is  not  demanded,  but  the  joints  should  be 
cióse  enough  to  prevent  leakage  of  the 
liquid  mass  which  will  bleed  the  concrete 
of  any  material  portion  of  its  cement. 

Beveling  Strips  and  Moldings. — When 
beveled  or  rounded  edges  are  specified,  see 
that  the  proper  beveling  strips  or  moldings 


INSPECTION    OF    FORM    WORK. 


31 


are  placed  in  the  forms.  This  is  a  minor 
detail,  very  likely  to  be  overlooked  by  car- 
penters. 

Spacing  and  Squaring  Column  Molds. 

See  that  column  molds  are  accurately 
spaced  in  all  directions  and  that  they  are 


¿Y?<?/r-  ¿?o/?f/: 

Fig.  1 — Correct 


Fig.    2 — Incorrect. 


set  square  with  the  lines  laid  down  on  the 
plans.  Figures  1,  2  and  3  indícate  the  kind 
of  errors  in  spacing  and  squaring  that 
should  be  watched  for. 


Fig.   'ó — Incorrect. 


Cleaning  Column  Molds. — See  that  the 
column  molds  are  cleaned  with  scrupulous 
care.     The  bottoms  of     column  molds     are 


32  CONCRETE    1NSPECTI0N. 

particularly  likely  to  get  the  sweepings 
from  girder  boxes  and  other  debris,  and 
they  are  particularly  hard  to  clean  unless 
special  provisión  is  made  for  cleaning.  A 
good  practice  is  to  require  the  bottom  of 
the  mold  to  be  left  open  on  one  side  un- 
til  ready  to  pour  the  concrete.  This  open- 
ing  gives  access  for  cleaning,  permits  ex- 
amination  for  cleanliness  and  gives  light 
by  which  the  lodging  of  sticks  or  blocks 
in  the  reinforcement  can  be  detected  by 
peering  up  through  the  mold. 

Camber  of  Beam  Forms. — See  that  beam 
and  girder  boxes  are  given  a  camber  to 
provide  for  settlement  under  load.  By 
camber  is  meant  making  the  box  slightly 
higher  at  mid  span  than  at  the  ends.  A 
common  camber  is  l/2  in.  for  every  10 
ft.  of  span. 

Wire  Ties  and  Spacers. — See  that  the 
wire  ties  for  wall  forms  are  in  place  and 
are  made  taut  so  as  to  pulí  the  sides  cióse 
against  the  spacers.  The  form  of  tie 
shown  by  Fig.  4  is  the  best.  See  that 
the  spacers  are  removed  from  the  forms 
as  soon  as  the  concreting  reaches  them. 
Careless  or  lazy  workmen  will  often  sim- 
ply  knock  them  out  and  leave  them  embed- 
ded  in  the  wall,  or  bury  them  as  they 
stand. 

Prcjecting  Ends  of  Wire  Wall  Ties. — 
See  that  the  projecting  ends  of  wire  ties 
used    to    hold    together    the    sides    of   wall 


INSPECTION    OF    FORM    WORK. 


33 


forms  and  left  embedded  in  the  concrete 
are  cut  off  smoothly  and  flush  with  the 
face  of  the  wall.  A  rust  spot  invariably 
forms  on  the  face  of  the  wall  where  the 
tie  is  cut  off  so  that  such  ties  should 
not  be  used  where  the  presence  of  rust 
spots  is  prohibited. 


m'. 


5pocer.  ¿ 


A  5 pocen j. 


¿hp/:-  Confr. 


Fig.  4 — Wire  Tie  For  Forms. 


H¡>/<í. 


Bolt  Ties  and  Spacers — See  that  the  bolts 
are  tightened  against  spacers  set  between 
the  two  sides  of  the  forms  inside.  See 
that  the  bolts  are  enveloped  inside  the 
form  with  sleeves  or  are  thoroughly 
greased,  otherwise  the  bolt  will  stick  and 
can  be  drawn  out  only  by  wrenching  and 
tearing  the  concrete,  and  perhaps  cannot 
be  removed  at  all.  See  that  bolt  ties  are 
not  located  cióse  to  a  córner  or  face  or 
the  concrete  may  be  spalled  off  in  pulling 
them. 

Anchoring  Pyramidal  or  Batter  Forms. 
— See  that  forms  for  retaining  walls   with 


34  CONCRETE    INSPECTION. 

battered  sides,  pyramidal  forms  for  column 
footings,  etc.,  are  firmly  anchored  down 
to  resist  the  up-thrust  or  floating  effect 
of   the    semi-liquid    concrete. 

Arch  Centers. — See  that  arch  centers 
are  framed,  assembled  and  erected  in  a 
workmanlike  manner.  See  that  substantial 
foundations  are  provided  for  the  center.  See 
that  suitable  means  are  provided  for  strik- 
ing  or  lowering  the  center  gradually  and 
without  shock  or  jar  to  the  concrete.  See 
that  allowance  is  made,  in  erecting  centers, 
for  settlement  under  load  and  for  perma- 
nent  camber.  See  that  the  lagging  is  of 
even  thickness  and  is  made  smooth  to  give 
a  good  surface  to  the  soffit  of  the  arch. 

Forms  for  Arch  Sections. — See  that 
suitable  forms  are  provided  to  hold  in 
place  sections  of  arch  ring  being  concret- 
ed.  If  the  concreting  is  done  in  longi- 
tudinal sections  see  that  the  forms  are  set 
vertical  and  parallel  with  the  face  of  the 
arch.  If  .  the  concreting  is  done  in 
transverse  sections  see  that  the  forms  are 
set  in  radial  planes  and  straight  across  the 
arch  at  right  angles  to  the  faces. 

Molds  for  Ornaments. — See  that  the 
molds  are  so  constructed  that  they  can 
be  removed  piece  by  piece  without  injur- 
ing  the  casting.  See  that  their  strength 
and  rigidity  is  ampie  to  withstand  tamp- 
ing  and  other  strains  without  distortion. 

Time  of  Removing  Forms. — See  that 
forms  are  not  removed  until  the  concrete 


INSPECTION    OF    FORM    WORK.  35 

is  capable  tinder  the  conditions  of  stand- 
ing  safely  without  support.  The  setting 
and  hardening  of  concrete  are  variable  fac- 
tors  depending  on  the  cement,  the  tempera- 
ture,  etc.,  and  set  rules  cannot  be  made 
for  time  of  removing  forms.  Specifications 
often  state  the  mínimum  time  after  con- 
creting  for  removing  forms ;  where  they 
do  not  state  this  time  the  inspector  should 
ascertain  the  ideas  of  the  engineer  and  in 
important  cases  had  better  obtain  specific 
orders  from  the  engineer.  The  forms  should 
not  be  removed  until  the  concrete  which 
they  support  has  been  examined  for  hard- 
ness ;  the  concrete  should  not  only  be  hard, 
but  should  ring  when  struck  with  a  ham- 
mer.  Forms  should  remain  longer  under 
beams  and  arches  than  around  columns  or 
walls,  and  longer  under  beams  and  arches 
of  long  spans  than  of  short  spans.  Forms 
should  remain  in  place  longer  if  the 
weather  is  cool  and  damp  than  if  it  is 
warm  and  dry.  To  sum  up,  the  time  for 
removing  forms  is  that  time  when,  in  the 
best  judgment  of  the  engineer,  the  con- 
tractor and  the  inspector,  they  can  be  re- 
moved without  injury  or  danger  to  the 
concrete  which  they  support.  The  follow- 
ing  are  the  times  for  removing  forms  prac- 
ticed  by  one  competent  firm  of  contract- 
ors: 

Walls  in  mass  work,  1  to  3  days,  or 
when  the  concrete  will  bear  pressure  of 
the  thumb  without  indentation. 


36  CONCRETE    INSPECTION. 

Thin  walls,  in  summer,  2  days;  in  cold 
weather,  5  days. 

Slabs  up  to  6-ft.  span,  in  summer,  6 
days ;   in  cold  weather,  2  weeks. 

Beams  and  girders  and  long  span  slabs, 
in  summer,  10  days  or  2  weeks;  in  cold 
weather,  3  weeks  to  1  month.  If  shores 
are  left  without  disturbing  them,  the  time 
of  removal  of  the  sheeting  in  summer  may 
be   reduced   to    1    week. 

Column  forms,  in  summer,  2  days ;  in 
cold  weather,  4  days,  provided  girders  are 
shored  to  prevent  appreciable  weight  reach- 
ing  columns. 

Conduits,  2  or  3  days,  provided  there  is 
not  a  heavy  fill   upon  them. 

Arches  of  small  size,  1  week;  for  large 
arches  with  heavy  dead  load,  1  month. 

Method  of  Removing  Forms. — See  that 
the  method  of  removing  forms  is  one 
which  does  not  jar  or  chip  the  concrete 
or  bring  sudden  shocks  on  the  molded 
members.  See  that  prying  with  bars  and 
sledging  is  not  resorted  to;  if  the  forms 
are  properly  designed  and  constructed  nei- 
ther  is  necessary.  See  that  the  forms 
when  being  taken  down  are  not  dropped 
onto  floors  and  banged  against  columns 
and  walls.  See  that  a  regular  procedure 
is  followed  in  removing  forms,  and  if 
possible  have  the  work  done  by  regular 
gangs  so  that  the  men  become  trained  in 
the  requirements  and  methods  of  the 
work. 


INSPECTION    OF    FORM    WORK.  37 

Removing  Column  Forms. — See  that 
column  forms,  if  removed  first,  are  so  re- 
moved as  not  to  disturb  the  beam  and 
slab  forms.  Column  forms  may  safely  be 
removed  considerably  before  beam  and  slab 
forms,  and  it  is  wise  to  do  so  both  to  give 
the  air  access  to  the  concrete  and  to  en- 
able  the  columns  to  be  inspected  for  faults 
before  any  load  is  brought  onto  them,  but 
if  the  removal  of  column  forms  necessi- 
tates  loosening  or  shifting  the  beam  and 
slab  forms  they  should  not  be  disturbed 
until  it  is  time  safely  to  remove  the  beam 
and  slab  forms. 

Removing  Beam  Forms. — See  that  the 
bottom  of  the  beam  form  remains  in  place 
until  after  the  side  forms  have  been  re- 
moved. This  permits  the  sides  of  the  beam 
to  be  exposed  for  inspection  and  to  the 
curing  action  of  the  air  without  lessening 
the  support  of  the  beam  against  collapse. 

Striking  Centers. — See  that  arch  centers 
are  not  struck  or  removed  in  less  than  the  ' 
specified  time  after  concreting  is  finished. 
If  the  specifications  do  not  stipulate  this 
time  get  instructions  from  the  engineer. 
See  that  centers  are  removed  without  shock 
or  jar  to  the  arch  ring.  See  that  centers 
particularly  for  long  spans  are  lowered 
evenly  and  very  gradually,  so  as  to  allow 
the  ring  to  settle  slowly  and  uniformly. 
For  very  long  span«-  the  engineer  will 
usually  provide  speciai  directions  for  strik- 
ing centers. 


38 


CONCRETE    INSPECTION. 


Swelling  of  Forms. — See  that  the  forms 
are  so  framed  that  swelling  will  not  frac- 
ture the  concrete  or  prevent  easy  removal. 
For  example  in  molding  walls  having  face 
panels  or  moldings,  long  continuous  studs 
cut  to  the  profile  of  the  wall  face  will  by 
swelling  and  the  weight  of  the  concrete  be 
difficult  to  remove  without  fracturing  cor- 


¿y?tf/r-  Cbs?fr. 

Fig.    5 — Sketch    Showing   a    Method    oí    Pro- 
viding   for  Swelling  of  Lagging. 

ners  and  edges  of  the  panels  or  moldings. 
The  swelling  of  lagging,  as  ordinarily 
formed,  will  do  little  more  than  "take  up" 
the  joints;  too  well  seasoned  lumber  should 
not  be  used  for  lagging.  When  dangerous 
swelling  of  lagging  may  be  anticipated,  a 
single  narrow  lagging  board  may  be  ar- 
ranged  to  be  withdrawn  after  initial  set  in- 
to  notches  left  in  the  studding  (Fig.  5), 


INSPECTION    OF    FORM    WORK.  39 

thus  leaving  an  open  space  to  take  up  the 
expansión. 

Bracing  of  Forms. — See  that  all  forms 
are  securely  braced :  (1)  to  withstand  the 
loads  that  come  upon  them;  (2)  to  pre- 
serve their  alinement.  Bracing  is  frequent- 
ly  done  carelessly  and  must  be  watched  par- 
ticularly  in  regard  to  its  sufficiency  to  pre- 
serve accurate  alinement.  See  that  the  braces 
are  firmly  fixed  at  the  foot  and  top  and 
that  they  are  stiff. 

Location  of  Shores. — See  that  shores  are 
not  located  hap-hazard.  They  should  come 
at  mid-span,  one-third  span,  quarter-span, 
etc.,  points.  See  that  shores  in  each  story 
are  located  over  the  shores  in  the  story  be- 
low. 

Length  of  Shores. — See  that  shores  are 
cut  to  proper  length  for  the  work.  If 
much  too  short  excessive  blocking  up  is 
necessitated  and  the  support  is  Hable  to  be 
unstable;  if  too  long  they  have  to  be  hard 
driven  into  place  with  danger  t  the  form- 
work,  the  length  should  be  just  such  that 
the  cap  and  footing  pieces  can  be  placed 
and  the  double  wedges  can  be  started  and 
tightened. 

Square  Ends  on  Shores. — See  that  the 
ends  of  shores  are  sawed  off  square  so  as  to 
have  uniform  bearing  on  wedges. 

Wedges. — See  that  uprights  supporting 
centers,  girder  boxes,  etc.,  are  set  on  double 
wedges. 


40  CONCRETE    INSPECTION. 

Footings  for  Shores. — See  that  ampie 
footings  are  used  under  posts  to  distribute 
the  load  over  soft  ground  or  green  con- 
crete. 

Caps  for  Shores. — See  that  posts  used 
to  support  floor  slabs  or  beams  after  the 
forms  have  been  removed  are  capped  with 
plank  or  scantling  to  distribute  the  pres- 
sure. 

Time  of  Removing  Shores. — See  that 
shores  for  floors,  girders,  or  arches  are  not 
removed  before  the  time  specified.  If  time 
is  not  specified  secure  instructions  from  the 
engineer.  In  ordinarily  good  weather  shores 
should  remain  in  place  two  weeks,  in  cold. 
damp  weather  four  weeks.  For  extra  long 
spans  the  time  should  be  longer.  The  prop- 
er  time  for  removing  shores  is  a  matter  of 
good  judgment;  omit  no  precaution  to 
ensure  safety, 

Method  of  Removing  Shores. — See  that 
shores  are  removed  without  shock  or  jar 
by  pulling  the  double  wedges  at  the  bottom. 
See  that  the  shores  are  not  removed  one  at 
a  time  and  then  replaced ;  this  is  sometimes 
done  to  permit  removal  of  bottom  boards 
of  beam  molds.  etc.,  before  final  removal  of 
shores.  See  that  the  shore  is  lowered 
gently  and  not  allowed  to  drop  heavily  onto 
the  floor  below.  When  shores  are  finally 
removed  see  that  they  are  taken  out  for  a 
beam  or  a  panel  at  a  time;  do  not  permit 


INSPECTION    OF    FORM    WORK.  41 

all  the  shores  under  a  floor  to  be  knocked 
down  rapidly  in  succession. 

Runways. — See  that  runways  are  not 
laid  directly  on  the  steel  but  are  sup- 
ported  above  the  steel  by  horses  or 
trestles. 


CHAPTER     IV.      INSPECTION     OF 
REINFORCEMENT. 

Concrete  is  weak  in  tensión,  i.  e.,  a 
strain  tending  to  pulí  it  apart,  but  it  is 
strong  in  compression,  i.  e.,  a  strain  tend- 
ing to  crush  it  together.  Reinforcement  is 
the  steel  rods,  bars,  or  netting  inserted  in 
concrete  to  make  up  for  its  weakness  in 
tensión.  Their  number,  size  and  spacing 
are  computed  by  the  engineer  so  as  exactly 
to  supply  the  lacking  tensile  strength  in  the 
concrete  member  being  designed.  If  either 
number,  size  or  spacing  is  varied  from, 
the  strength  of  the  concrete  member  is  not 
what  it  was  designed  to  be  and  injury  re- 
sults.  The  inspector's  first  duty  is  to  see 
that  no  detail  of  the  engineer's  design  of 
reinforcement  is  varied  from  in  construc- 
tion — this  duty  is  imperative. 

Checking,  Assorting  and  Storing  Steel. 
— See  that  as  the  steel  is  received  it  is 
checked,  assorted  and  stored  in  such  a  man- 
ner  that  it  can  be  readily  inspected,  that  it 
is  reasonably  protected  from  rust,  dirt,  oil, 
paint,  etc.,  and  that  those  portions  needed 
first  may  be  reached  without  disturbing 
the  remainder. 

Assembling  of  Reinforcement.  —  See 
that  in  the  assembling  of  the  reinforce- 
ment  the   exact   number,   size,   form,   spac- 

42 


UNIVERSJTY    1 

INSPÉCTlüN  ~OFREINFORCEMENT.       43 


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fe  con  :r 
p'iberlpH 
Jer   oJ 
y  the  ei:    i 
*:  r«  | 

i. i  ar  y      i 
5n;rinei,,¿B 

■HIH  w 

;ir    s     i 
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ni 

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'! 

i4  CONCRETE    INSPECTION. 

Bending  of  Bars. — See  that  the  bending 
of  bars  is  done  in  such  a  manner  that  they 
do  not  break  or  crack  at  the  bend.  The 
bending  forcé  should  be  applied  gradually 
and  not  with  a  jerk.  Cold  bending  is  al- 
ways  preferable ;  if  hot  bending  is  allowed 
see  that  the  bending  is  not  so  done  that 
the  bar  is  weakened  or  burned.  See  that 
the  bends  are  aecurate  in  line  and  plañe ; 
the  accompanying  sketch,  Fig.  6,  shows  the 


f/evat/on 
c 


t f 


c     .     „  P/O/7 

£s?gr-Contr 

Fig.    6 — Sketch    Showing    Coramon    Error    in 
Bending  Reinforcing  Bars. 

nature  of  the  error  to  be  watched  for,  the 
bends  are  not  all  in  one  plañe  a  f,  but  the 
one  at  d  is  twisted  to  one  side  d  e   f. 

Splicing  of  Bars. — See  that  the  splicing 
of  bars  is  done  exactly  according  to  the 
engineer's  plans.  Various  forms  of  splices 
are  in  use  and  if  not  definitely  instructed 
by  the  plans  and  specifications  the  inspector 
should  learn  from  the  engineer  what  form 
or    forms    will   be    acceptable. 

Protruding  Ends  of  Bars. — See  that  the 
ends  of  bars  which  are  left  protruding  for 
splicing  are,   if  they  are   likely   not   to  be 


INSPECTtON  OF  REINFORCEMENT.       45 

connected  up  for  some  little  time,  painted 
with  cement  paint  to  diminish  rusting  and 
so  gnarded  that  they  are  not  bent  down 
or  knocked  loóse. 

Fastening  Reinforcement. — See  that  all 
reinforcement  is  securely  fastened  to  pre- 
serve spacing,  location,  alignment,  etc. 
Braces,  blocks,  suspenders,  spacers,  ties, 
etc.,  shotild  be  used  in  ampie  number  to 
make  certain  of  this  feature.  See  that  all 
temporary  fastenings  are  removed  as  fast 
as    the    concreting    reaches   them. 

Wiring  Reinforcement. — See  that  the 
wiring  of  reinforcement  at  intersections  is 
done  carefully  and  strongly.  Soft  black 
iron  wire,  No.  1G  to  No.  18  gage,  should 
be  used  and  the  ties  should  be  made  taut 
and  be  well  fastened. 

Placing  Column  Reinforcement. — See 
that  the  reinforcing  frame  is  concentric 
with  that  of  the  column  below,  that  the 
bars  are  vertical,  that  all  ties  are  in  place 
and  are  taut,  that  all  splices  are  made,  and 
that  no  part  of  the  steel  touches  the  walls 
of  the  form  but  that  there  is  uniform  open 
space  all  around  between  the  steel  and  the 
form. 

Spacing  Column  Bars. — See  that  tem- 
plets  are  used  particularly  at  bottom  and 
top  to  insure  accurate  spacing  of  column 
bars.  This  is  necessary  to  ensure  that  the 
bars  of  successive  columns  will  fit  when 
spliced.     If  the  bars  are  bent  as  shown  by 


40 


CONCRETE    INSPECTION. 


Fig.  7,  to  connect  with  the  bars  of  the 
column  above,  the  spacing  should  be  veri- 
fied  with  particular  care.* 

Tying  Column  Bars.— -See  thatthewire 
ties  or  hoops  holding  the  vertical  bars  are 
tant,  or,  if  punched  straps  or  hooked  bars 


inq'n-Confr. 

Fig.   7 — Sketch   Showing  Bending  of   Column 
Bars    at    Connections. 


are  used,  that  they  fit  exactly.  See  that 
the  vertical  spacing  of  the  ties  is  exact  and 
according  to  plans.  Figure  8  shows  cor- 
rect  and  incorrect  way  of  fastening  ties. 


*The  connection  shown  by  Fig.  7  has  been 
and  is  used  by  some  designers  which  is  the 
reason  for  calling  attention  to  the  bar  splic- 
ing.  The  author  considers  this  to  be  an  ex- 
ample  of  bad  detailing  which  should  never 
be  employed.  All  column  reinforcement 
should  be  perfectly  straight.  One  way  to 
accomplish  this  is  to  set  the  steel  in  the 
lower  columns  closer  to  the  inside  so  that 
in  the  top  columns  it  will  be  within  the  re- 
quired  distance  of  the  face.  The  best  posi- 
tion  anyway  is  near  the  center. 


INSPECriON  OF  REINFORCEMENT.       47 


Splicing  Column  Bars. — See  that  column 
bars   are  spliced  exactly  according   to  the 


»í¿\0\  *'*.•* 


o; 


SvS 


31? 


£ngr-  Contr. 

Fig.  8 — Showing  Correct  and  Incorrect  Meth- 
od  of  "Tying"  Column  Bars. 


£/?(¡r-  Contr 


Fig.  9 — Sketch  Showing  Typical  Column  Bar 
Splices. 


48  CONCRETE    INSPECTION. 

plans.  If  a  butt  joint  is  specified  see  that 
the  butting  ends  are  square  and  the  bear- 
ing  uniform  and  that  the  joint  is  held  true 
to  line  by  sleeves  or  splice  bars.  If  lap 
joints  are  allowed  see  that  the  wire  wrap- 
ping,  cable  splices,  etc.,  are  made  taut  and 
secure.  Various  styles  of  column  splices 
are  shown  by  Fig.  9.  The  splice  is  a  vital 
point  and  should  be  watched  with  care.* 
Placing  of  Beam  Reinforcement. — See 
that  beam  reinforcement  is  placed  sym- 
metrical  with  the  axis  of  the  beam,  that  the 
bottom  bars  are  held  the  required  height 
above  the  bottom  of  the  beam,  that  the 
proper  space  is  maintained  between  the 
reinforcement  and  the  sides  of  the  beam, 
that  the  required  connections  are  made  at 
the  ends  of  beam  with  the  column  bars 
or  the  reinforcement  of  abutting  beams  or 
walls,  that  all  planes  and  lines  are  true,  and 

*The  splices  illustrated  are  all  used  by  de- 
signers.  The  author  does  not  favor  splicing 
column  bars  except  by  butt  joints  or  by 
screwing  the  rods  together  within  sleeves. 
He  would  eliminate  all  the  splices  shown  ex- 
cept the  one  on  the  extreme  left  in  Fig.  9. 
A  better  way  (if  butt  joints  are  not  used) 
is  to  let  the  rods  from  the  lower  columns 
project  up  into  the  upper  column  about  2 
ft.  Beside  them  set  pieces  about  4  ft.  long 
going  into  the  top  of  the  lower  columns  2 
ft.  and  into  the  upper  columns  2  ft.  These 
bars  will  span  the  joint.  Then  set  the  steel 
for  the  upper  column  and  remember  to  leave 
between  the  bars  at  these  joints,  an  amount 
of  concrete  such  as  is  generally  required  in 
beams;  that  is,  the  distance  between  pieces 
of  steel  should  be  equal  to  iy2  times  the 
thickness  at  least.  Wiring  and  splicing  col- 
umn reinforcement  introduces  danger  of 
eccentric  loading  and  splitting  of  the  con- 
crete. 


INSPECTION  OF  REINFORCEMENT.       49 

that  all  parts  of  the  reínforcement  are 
wired  together  or  otherwise  held  firmly  to 
position. 

Placing  Wall  Reínforcement. — See  that 
the  reínforcement  is  placed  the  required 
distances  from  the  faces  of  the  wall  and  in 
the  exact  planes  laid  down  in  the  engineer's 
plans.  See  that  the  stipulated  spacing  of 
the  bars  is  accurately  followed.  See  that 
the  bars  are  straight  and  true  to  line. 

Placing  Ccnduit  Reínforcement. — See 
that  the  spacing  of  bars  is  according  to 
plan,  that  the  planes  of  the  circumferential 
bars  are  perpendicular  to  the  axis  of  the 
conduit,  that  the  alinement  of  the  longitudi- 
nal bars  is  parallel  to  the  axis  of  the  con- 
duit, that  the  reínforcement  as  a  whole  is 
concentric  with  the  axis  of  the  conduit  and 
conforms  exactly  to  the  circumferential 
curve  called  for  by  the  engineer's  plans. 

Placing  Reínforcement  for  Circular 
Tanks. — See  that  the  spacing  of  bars  is 
according  to  plan,  that  the  circumferential 
rings  are  true  circles,  that  splices  are  ac- 
cording to  plans  and  are  made  with  par- 
ticular care,  and  that  the  reínforcement  as 
a  whole  is  concentric  with  the  vertical  axis. 


CHAPTER  V.  INSPECTION  OF 
CONCRETING. 
A  decade  ago  when  dry  and  médium 
mixtures  were  almost  entirely  used,  speci- 
fications  invariably  required  that  concrete 
should  be  deposited  in  uniform  horizontal 
layers  and  that  each  layer  should  be  thór- 
oughly  tamped.  When  dry  and  médium 
mixtures  are  used  this  is  still  the  invariable 
rule  of  procedure.  Much  and  probably 
most  of  the  concrete  work  done  at  the 
present  time  is  done  with  very  wet  mix- 
tures that  cannot  be  tamped,  and  pouring 
and  puddling  are  now  the  methods  of  plac- 
ing  and  compacting  concrete.  The  filling 
still  naturally  takes  the  form  of  horizontal 
courses,  but  there  is  no  distinction  between 
individual  courses  as  is  the  case  with  sepa- 
rately  tamped  layers  of  dry  concrete.  The 
pouring  is  done  at  different  points  of  the 
área  to  be  filled,  both  because  the  flow  of 
even  sloppy  concrete  is  sluggish  and  time 
is  saved  by  pouring  at  several  points,  and 
because  a  streaky  concrete  is  likely  to  re- 
sult  if  flowing  from  a  single  pouring  point 
is  entirely  depended  upon  to  fill  the  forms. 
Puddling  or  slicing  take  the  place  of  tamp- 
ing  and  consist  in  churning  and  cutting  the 
wet  mixture  with  rods  or  slice  bars  to 
work  out  air  bubbles,  cióse  up  pockets,  and 
settle  the  materials. 

50 


INSPECTION    OF    CONCRETING.  51 

Depositing  in  Buckets. — See  that  buckets 
just  clear  the  work  when  discharged;  a 
drop  (1)  jars  the  forms  and  may  displace 
the  reinforcement  and  (2)  tends  to  pro- 
duce separation  of  the  stone  from  the  mor- 
tar.  See  that  the  bucket  is  not  allowed  to 
rest  on  the  reinforcement  and  in  swinging 
does  not  accidentally  hit  the  forms  or  sta- 
ging.  See  that  the  bucket  does  not  leak 
and  spill  concrete  over  the  work. 

Depositing  Through  Chutes. — See  that 
segregation  or  separation  of  the  stone  from 
the  mortar  does  not  occur  in  depositing 
concrete  through  chutes.  Fear  of  segrega- 
tion causes  engineers  generally  to  object  to 
chuting  concrete  into  place.  The  inspector, 
of  course,  will  be  governed  by  the  engi- 
neer's  decisión  in  the  matter.  As  a  matter 
of  fact,  however,  concrete  can  be  depqsited 
safely  through  chutes  and  prejudice  against 
the  method  is  gradually  disappearing. 

Method  of  Pouring. — See  that  the  pour- 
ing  is  done  at  several  points  over  the  área 
to  be  filled  so  as  to  reduce  flowing  and 
spreading  to  a  mínimum.  See  that  the 
pouring  is  so  regulated  that  the  rush  of  the 
semi-liquid  concrete  does  not  sweep  the  re- 
inforcement out  of  place.  See  that  shock 
due  to  too  sudden  discharge  is  avoided. 

Time  of  Pouring. — See  that  the  time 
elapsing  between  mixing  and  pouring  the 
concrete  is  well  within  the  time  of  set  of 
the  cement.  As  a  rule  the  elapsed  time 
should  not  exceed  30  to  60  minutes;  some 
specifications  restrict  it  to  10  minutes. 

Tamping  Dry  and  Médium  Concrete. — 
See  that  the  concrete  is  deposited  in  even 


52  CONCRETE    JNSPECTION. 

layers  not  to  exceed  6  to  8  ins.  in  thickness 
and  is  thoroughly  tamped  with  tampers 
heavy  enough  to  thoroughly  compact  the 
concrete  and  bring  a  film  of  water  to  the 
surface,  if  a  dry  mixture  is  used,  and  to 
cause  the  mass  to  quake  under  the  blow  if 
a  médium  mixture  is  used.  If  reinforced, 
see  that  the  tamping  is  done  with  particular 
care  to  get  the  concrete  around  and  into 
cióse  contact  with  all  reinforcing  metal  and 
so  as  not  to  displace  the  reinforcement. 

Puddling  Wet  Concrete.— See  that  the 
puddling  is  thoroughly  done  so  as  to  work 
out  air  bubbles  and  pockets  and  bring  the 
concrete  into  cióse  contact  with  the  rein- 
forcement at  every  point.  See  that  the 
poles  or  slice  bars  are  small  enough  to 
enter  well  into  the  spaces  between  and 
around  the  reinforcement.  See  that  care  is 
used  not  to  strike  the  reinforcement  and 
displace  it. 

Pouring  Slabs. — See  that  the  full  thick- 
ness of  floor  and  roof  slabs  is  poured  in 
one  continuous  operation  and  that  the  con- 
crete is  got  well  under  the  slab  reinforce- 
ment.* If  possible,  slab  and  beam  should 
be  poured  in  one  continuous  operation. 


*To  make  certain  that  the  bars  are  cov- 
ered  underneath  some  engineers  require  that 
a  layer  of  concrete  be  spread  over  the  slab 
centers  and  that  the  reinforcing  net  or 
bars  be  laid  on  top  of  it.  Where  wire  mesh 
or  expanded  metal  slab  reinforcement  is 
used  working  the  concrete  underneath  it  can 
be  facilitated  by  lifting  the  mesh  slightly 
by  means  of  bars  having  a  hook  at  one  end. 


INSPECTION    OF    CONCRETING.  53 

Pouring  Beams. — See  that  beams  are 
poured  in  one  continuous  operation  from 
bottom  to  top;  that  the  concrete  is  worked 
closely  around  the  reinforcement  and  into 
corners  by  thorough  puddling;  that  the 
stone  is  worked  back  from  the  sides  to  per- 
mit  the  mortar  to  flow  to  the  faces  and  give 
a  smooth  surface  when  set;  that  the  space 
between  the  bottom  of  the  mold  and  the 
bottom  reinforcing  bars  is  tightly  filled.  If 
possible  beam  and  slab  should  be  poured 
in  one  continuous  operation. 

Pouring  T-Beams. — See  that  when  beam 
and  slab  are  designed  to  act  together  as  a 
T-beam  that  both  are  poured  in  one  opera- 
tion. 

Pouring  Columns — See  that  columns  are 
poured  well  ahead  of  the  beams;  that  the 
pouring  is  a  continuous  operation*  from 
bottom  to  underside  of  supported  beam  or 
girder;  that  the  concerté  is  freed  from  air 
bubbles  and  worked  closely  around  the  re- 
inforcement and  into  corners  by  thorough 
puddling. 


"By  "continuous"  the  author  means  that 
no  delay  between  batches  long  enough  to 
permit  the  oíd  concrete  to  set  before  fresh 
concrete  is  added  should  be  permitted.  The 
best  way  to  pour  columns  is  as  follows:  Pour 
not  to  exceed  4  ft.  at  a  time.  Allow  not  less 
than  20  ñor  more  than  30  minutes  to  elapse 
before  pouring  another  4  ft.  Keep  stirring 
the  concrete  (churning  it)  while  pouring  and 
have  men  with  hammers  tapping  the  out- 
side  of  the  forms  while  pouring. 


54  CONCRETE    INSPECTION. 

Puddling  Columns — See  that  the  tampers 
used  in  concreting  columns  are  small 
enough  to  go  easily  between  the  outside 
of  the  reinforcement  and  the  inside  of 
the  form.  See  that  the  tampers  are  han- 
dled  carefully  so  as  not  to  strike  and  dis- 
place the  reinforcement. 

Places   for   Stopping   Concreting. — See 

that  concreting  is  stopped  for  the  night  or 
at  other  times  at  predetermined  points  and 
in  a  predetermined  manner.  If  any  unfor- 
seen  contingency  compels  concreting  to  be 
stopped  at  other  points  than  those  named 
as  permissable  use  every  precaution  in 
bonding  the  fresh  concrete  to  the  oíd  to 
secure  a  solid  joint. 

Stopping  Slabs. — Stop  the  concrete  in  a 
vertical  plañe  at  right  angles  to  the  span 
either  (1)  at  midspan,  or,  (2)  over  the 
center  of  the  supporting  beam  or  girder. 
Never  stop  the  concrete  in  a  horizontal 
plañe  at  partly  the  height  of  the  slab ; 
never  stop  the  concrete  where  the  shear 
is  great  near  the  end  of  the  span  or  under 
concentrated  load;  never  slope  the  joint, 
always  make  it  vertical.     (See   Fig.   10.) 

Stopping  Beams  and  Girders. — Stop  the 
concrete  in  a  vertical  plañe  at  right  angles 
to  the  length  of  the  beam  either  (1)  at 
midspan  or  (2)  over  the  center  of  the  sup- 
porting column.  Never  stop  the  concrete 
on  a  horizontal  plañe  at  partly  the  height 
of  the  beam;  never  stop  the  concrete  near 


INSPECTION    OF    CONCRETING.  55 


=LJ 


fft-.f-q-«'*-.T*«  •^•í*;a-fc^M 


WJMVJM 


^LJ 


13 


t'ng'r-  Contr 

Fig.    10— Methods    of    Stopping   Off   Concrete 
Slabs. 

the  ends  of  beams  where  the  shear  is 
great;  never  slope  the  joint,  always  make 
it  vertical.     (See  Fig.  11.) 


Correct. 


^'¿"¿-'.V  '«'  .'<,."  O'  ?0"'<3.  ,0'.  .O'-q  ÍJ< 

><  ■ »  o-.a  \a.  ó  ■  o  .  o-  ■»•■  6.  'o-.t-  o  j 


u 


o;o:| 

•;<?"''q.'.I 


Ihcorrect. 


Er?gr- ü?r?//r 


Correct. 

Fig.    11— Methods    of    Stopping    Off    Concrete 
Girders. 


56  concrete  inspection. 

Stopping  Columns. — Stop  column  at  the 
level  of  the  bottom  of  the  beam  or  girder 
which  it  supports  and  never  at  any  other 
place   unless   compelled. 

Stopping  Walls.— Stop  walls  in  vertical 
planes  across  the  wall  and  lócate  stop,  if 
practicable,  where  expansión  joints  are  to 
come. 

Joining  New  Concrete  to  Oíd. — See 
that  every  precaution  is  taken  to  secure 
good  bond  when  joining  fresh  concrete 
to  concrete  that  has  already  set.  The  sur- 
face  of  concrete  which  has  hardened  has 
a  skin  or  coating  to  which  fresh  concrete 
will  not  adhere.  This  skin  must  be  re- 
moved and  the  surface  prepared  for  the 
new  material.  The  following  methods  are 
employed : 

(1)  Treat  the  surface  with  an  acid 
wash,  such  as  "Ransomite,"  which  etches 
off  the  surface  skin.  Wash  all  the  acid 
off  with  plenty  of  puré  water  and  apply 
the  fresh  concrete,  thoroughly  tamped  in 
places.  The  thorougrT  removal  of  the 
remaining  acid  by  washing  with  puré  wa- 
ter  is   absolutely   essential. 

(2)  "For  connections  made  after  a 
lapse  of  24  hours  or  more,  break  back  the 
surface  concrete  to  firm  material  and  clean 
the  fresh  surface  with  steam,  air  blast 
or  forceful  water  streams,  so  as  to  remove 
all  fine,  loóse  material.  Satúrate  well,  but 
not   so   that   water   stands   on   the   surface 


INSPECTION    OF    CONCRETING.  57 

or  oozes  from  the  material.  Paint  com- 
pletely  with  neat  cement  grout,  mixed  to 
the  consistency  of  thin  cream,  just  before 
new  concrete  is  deposited,  and  see  that  the 
latter  is  of  proper  mixture,  containing  a 
proper  proportion  of  mortar,  which  should 
be  worked  against  the  joint  so  as  to  be 
certain  that  no  voids  exist  in  its  vicinity." 
— E.  P.  Goodrich. 

(3)  "For  connections  made  after  long  in- 
tervals,  so  that  the  oíd  cement  has  set  hard. 
and  where  the  expense  of  rough-pointing 
the  whole  surface  is  greater  than  is  re- 
quired  because  of  the  nature  of  the  desired 
bond,  use  commercial  muriatic  acid,  di- 
luted  with  clear  water,  1  to  5,  or  the  com- 
mercial bonding  powders,  dissolved  in  clear 
water  at  the  rate  of  5  Ib.  of  powder  to  10 
gals.  of  water.  First  wet  the  oíd  concrete 
surface  v/ith  so  much  water  that  a  fresh 
wetting  is  not  immediately  absorbed.  Re- 
move  any  excess  of  moisture,  and  when  the 
surface  appears  as  if  commencing  to  dry 
paint  on  the  oíd  surface  three  successive 
coats  of  acid,  one  after  the  other.  Let 
this  remain  for  about  30  minutes,  after 
which  carefully  clean  the  surface  of  un- 
spent  acid,  soluble  salts,  and  fine  material, 
with  plenty  of  water,  finally  cleaning 
with  a  steam  jet  or  air  blast  if  obtainable. 
Just  before  the  fresh  concrete  is  to  be  de- 
posited, and  while  the  oíd  material  is  still 
very  damp,  apply  a  thin  coat  of  neat  cem- 
ent grout  mixed  to  the  consistency  of  thin 


58  CONCRETE    INSPECTION. 

cream,  just  before  the  new  concrete  is  de- 
posited,  and  see  that  the  latter  is  of  proper 
mixture,  containing  a  proper  proportion  of 
mortar,  which  should  be  worked  against 
the  joint  so  as  to  be  certain  no  voids  exist 
in  this  vicinity.,, — E.  P.  Goodrich. 

Concreting  Connections. — See  that  par- 
ticular care  is  exercised  in  concreting  con- 
nections, such  as  the  juncture  of  a  column 
and  a  girder.  The  number  of  reinforcing 
rods  at  such  points  increases  the  liability  of 
void  spaces  among  and  around  the  bars. 

Coping  Construction. — See  that  copings 
for  walls  are  molded  particularly  straight 
and  true  to  grade.  The  coping  is  the  por- 
tion  of  the  wall  on  which  any  variation 
from  true  alignment  shows  most  objec- 
tionably,  and  its  alignment  should  be 
watched  with  particular  care.  Where  the 
body  of  the  wall  is  for  any  reason  slight- 
ly  out  of  true,  the  defect  can  be  largely 
corrected  by  capping  it  with  a  straight  and 
true  coping.  The  coping  form  should  be 
capable  of  alignment  independently  of  the 
wall  form  proper. 

Filling  Bolt  Holes.— See  that  holes  left 
in  the  wall  after  withdrawing  bolts  used 
for  wall  form  ties  are  closed  with  mortar 
well  forced  into  the  ends  of  the  hole  and 
troweled  off  flush  with  the  wall  face.  The 
"pointing"  must  be  carefully  done,  since 
the  grease  from  the  bolt  remaining  on  the 
walls  of  the  hole  makes  it  difficult  for  the 
mortar  to  stick. 


INSPECTION    OF    CONCRETING.  59 

Cutting  Finished  Concrete. — See  that 
steamfitters,  plumbers,  electricians,  etc.,  do 
not  cut  through  or  into  the  finished  con- 
crete in  placing  pipes,  wires,  etc.  The 
proper  holes,  channels,  etc.,  should  be  pro- 
vided  for  in  designing  the  work;  if  they 
are  not  provided  for,  consent  to  cut  them 
in  the  finished  work  should  come  direct 
from  the   engineer. 

Concreting  Arches. — See  that  the  arch 
ring  is  divided  into  sections  of  such  size 
that  the  concreting  of  each  section  can  be 
made  a  continuous  operation.  See  that  the 
concreting  is  made  a  continuous  operation 
for   each   section. 

Concreting  in  Transverse  Sections. — See 
that  the  sections  are  concreted  in  pairs, 
corresponding  sections  on  both  sides  of  the 
crown  being  concreted  simultaneously.  If 
tic  concreting  is  begun  at  the  skewback 
sections,  see  that  the  center  does  not  rise 
at  the  crown ;  weight  it  down  with  a  tem- 
porary  load  if  necessary.  The  better  prac- 
tice  is  to  concrete  the  crown  section  first 
and  work  toward  both  skewbacks  a  pair 
of  sections,  one  on  each  side,  at  a  time. 
In  arches  of  modérate  span  the  sections 
are  concreted  in  succession,  but  in  long- 
span  arches  altérnate  sections  are  con- 
creted. 

Concreting  in  Longitudinal  Sections. — 
See  that  the  concreting  is  begun  simulta- 
neously at  both  skewbacks  and  is  continued 
uniformly  and  continuously  to  the  crown. 


60  CONCRETE    1NSPECTION. 

Filling  Over  Arches. — See  that  the  ñll 
over  arches  is  not  put  in  too  soon  after 
concreting.  Generally  speaking,  two  weeks 
should  elapse  after  concreting  is  completed 
beíore  any  fill  is  placed  over  the  arch,  but 
conditions  sometimes  necessitate  shorten- 
ing  this  time.  In  such  cases  get  definite 
instructions   from  the  engineer. 

Drainage. — See  that  inserted  pipes,  gut- 
ters,  etc.,  intended  for  drainage  are  clear 
and  unobstructed.  Keep  such  channels 
plugged  or  protected  from  accidental 
choking  or  filling  with  concrete  or  other 
material  until  they  are  finally  covered  or 
capped. 

Expansión  Joints. — See  that  expansión 
joints  are  constructed  exactly  according 
to  the  engineer's  plans. 

Wetting  Finished  Work.— See  that  the 
concrete  after  the  removal  of  the  forms  is 
not  allowed  to  dry  out  too  rapidly.  When 
necessary  keep  the  surface  wcll  wet  by 
sprinkling,  coverings  of  wet  sand,  burlap, 
etc.  The  persistence  and  amount  of  sprink- 
ling required  will  depend  on  local  condi- 
tions; the  idea  is  to  prevent  the  water 
needed  for  hardening  the  concrete  from 
being  evaporated,  and  the  inspector's  judg- 
ment  must  be  exercised  to  determine  when 
and  what  amount  of  sprinkling,  etc.,  are 
necessary. 

Depositing  Concrete  Under  Water. — Se e 
that  the  concrete  while  being  deposited 
is    kept    as    free    as    possible    from    wash 


INSPECTIOX    OF    CONCRETING.  Gl 

which  will  float  off  the  fine  cement  from 
the  mixture.  See  that  the  concrete  is 
never  allowed  to  drop  loóse  through  any 
considerable  depth  of  water.  The  stand- 
ard methods  of  depositiñg  concrete  under 
water  are :  in  bags,  in  closed  buckets,  and 
through  tremies. 

Depositiñg  Thrcugh  Tremie. — A  tremie 
is  a  tube  of  wood  or  sheet  metal  long 
enough  to  reach  from  above  the  surface 
of  the  water  to  the  bottom;  it  is  operated 
by  filling  the  tube  with  concrete  and  keep- 
ing  it  full  by  successive  additions  while  al- 
lowing  the  concrete  to  flow  gradually  out 
at  the  bottom  by  raising  the  tube  slightly 
to  provide  the  necessary  opening.  See 
that  the  tremie  is  filled  full  before  allow- 
ing  any  concrete  to  flow  out  at  the  bottom, 
and  see  that  the  tremie  is  kept  full  as  long 
as  concreting  is  in  progress.  See  that 
the  tremie  is  moved  back  and  forth  so  as 
to  deposit  an  even  layer  over  the  área  to  be 
covered.  See  that  the  movement  of  the 
tremie  is  not  so  rapid  or  that  the  tremie 
is  not  raised  so  quickly  that  all  the  con- 
crete runs  out  and  is  "lost."  Every  time 
the  tremie  is  charged  anew  it  results  in 
washed  concrete  until  the  tube  is  again  full. 
A  concrete  that  is  mixed  not  quite  wet 
enough  to  be  plástic  works  best;  if  mixed 
very  wet  the  chance  of  "losing"  the  charge 
is  increased;  if  mixed  too  dry  it  is  more 
Hable  to  choke  in  the  tube. 

Depositiñg  in  Buckets. — Bottom   dump- 


62  CONCRETE    INSPECTION. 

ing  buckets  with  cióse  covers  are  best. 
The  idea  is  to  keep  the  concrete  closed 
away  from  the  water  until  it  is  finally  in 
place.  See  that  the  bucket  is  one  which 
will  dump  cióse  to  the  bottom»  and  that  in 
dumping  it  is  lowered  as  cióse  to  the  bot- 
tom  as  it  will  go.  See  that  the  bucket  is 
properly  closed  and  latched,  and  that  it  is 
lowered  vertically  to  the  bottom  as  rap- 
idly  as  practicable  and  is  dumped  without 
delay.  See  that  successive  bucketfuls  are 
deposited  so  as  to  form  as  nearly  as  pos- 
sible  uniform  layers  over  the  área  to  be 
covered.  Do  not  permit  isolated  piles  of 
concrete  to  be  placed. 

Depositing  in  Bags. — Fill  the  mixed  con- 
crete into  bags  of  gunnysack  or  other  por- 
ous  cloth  and  pack  the  bags  closely  into 
position.  The  bags  keep  the  cement  from 
free  wash  and  yet  when  placed  allov? 
enough  cement  to  ooze  through  the  meshes 
to  cement  the  whole  mass  together.  Paper 
bags  are  sometimes  used  in  place  of  cloth 
bags,  the  paper  breaking  open  when  soaked, 
so  that  the  sepárate  bagfuls  are  cemented 
into  one  mass.  See  that  the  bags  are  not 
filled  too  full  to  settle  readily  and  closely 
together  when  piled  in  place.  See  that 
the  bags  are  lowered  rapidly  through  the 
water  into  place  to  reduce  the  time  of 
wash.  See  that  no  delay  occurs  in  the 
process  of  depositing  which  will  permit 
concrete  in  place  to  become  set  before  suc- 
ceeding  bagfuls    are    deposited.       See   that 


INSPECTION    OF    CONCRETING.  63 

the  delay  between  mixing  the  concrete  and 
filling  and  depositing  the  bags  is  not  long 
enough  to  permit  the  concrete  to  have  set. 

Detecting  Wash. — The  existence  of 
"washing"  in  concrete  deposited  under  wa- 
ter is  shown  by  the  rising  to  the  surface 
of  a  milky  scum  (laitance.)  The  presence 
or  absence  of  laitance  indicates  quite  clear- 
ly   the   presence   or  absence   of   "washing." 

Protection from  Currents. — Where  there 
are  currents  a  dangerous  amount  of  wash- 
ing may  result  after  the  concrete  is  in 
place.  The  only  remedy  in  such  cases  is 
to  deflect  or  break  the  current  by  shields 
or  other  means,  and  the  means  adopted 
must  be  determined  for  each  case  sepa- 
rately.  The  inspector  should  watch  for 
trouble  of  this  sort  and  promptly  notify 
the  engineer  when  it  appears. 

Rubble  Concrete. — See  that  the  rubble 
stones  are  solidly  and  completely  imbedded 
in  the  concrete.  When  the  rubble  stones 
are  irregular  in  shape  a  sloppy  concrete 
must  be  used  to  get  them  thoroughly  em- 
bedded;  if  the  stones  have  fíat  beds  they 
can  be  laid  upon  layers  of  dry  concrete  and 
have  the  vertical  interstices  filled  with  dry 
concrete  by  tamping.  See  that  the  rubble 
stones  are  well  joggled  or  worked  to  a 
good  bed  with  crow  bars,  and  that  ver- 
tical spaces  are  prodded  and  puddled  to 
prevent  arching  and  voids. 


64  CONCRETE    INSPECTION. 

CONCRETING    IN     FREEZING 
WEATHER. 

Concrete  work  can  be  safely  done  in 
freezing  weather  if  precautions  are  taken 
to  counteract  the  action  of  frost.  Three 
methods  are  commonly  employed  to  accom- 
plish  this  result:  (1)  Add  some  substance 
to  the  mixing  water  which  produces  a 
brine  or  emulsión  which  freezes  at  some 
temperature  below  32°  R,  determined  by 
the  substance  added  and  the  richness  of 
the  brinc.  (2)  Heating  the  concrete  ma- 
tcrials  so  as  to  delay  the  action  of  frost 
until  the  concrete  has  had  time  to  set. 
(3)  Housing  in  the  work  and  supplying  ar- 
tificial heat  until  the  concrete  has  had  time 
to  set.  Any  combination  of  these  three 
methods  may  also  be  employed.  Methods 
one  and  two  have  rather  narrow  limita- 
tions  of  eftkiency,  but  the  third  method 
can  be  used  with  any  degree  of  frost.  Its 
cost  is  great,  however,  so  that  it  is  em- 
ployed only  under  special  conditions. 

Adding  Substances  to  Mixing  Water. — 
See  that  no  substance  is  added  to  the  mix- 
ing water,  the  effect  of  which  on  the  con- 
crete is  not  well  known.  If  any  other  sub- 
stance than  sodium  chloride  (common  salt") 
or  calcium  chloride  is  proposed  for  the 
purpose,  see  that  the  approval  of  the  engi- 
neer  is  had  before  its  use  is  permitted. 

Salt  in  Mixing  Water. — See  that  the 
amount  of  salt  used  in  mixing  water  to 
reduce  the  freezing  temperature  does  not 


1NSPECTI0N    OF    CONCRETING.  65 

cxceed  in  amount  10  per  cent  by  weight 
of  the  water.  Tests  show  that  the  strength 
of  cement  is  injuired  when  mixed  with  wa- 
ter having  an  excess  of  10  per  cent  by 
weight  of  added  salt.  It  is  wise  to  keep 
the  salt  well  below  10  per  cent.  See  that 
the  salt  addition  is  determined  by  actual 
weight ;  such  determinations  as  enough  salt 
to  "float  an  egg"  or  to  "float  a  potato" 
are  untrustworthy — it  takes  15  per  cent  of 
salt  to  "float  an  egg."  A  good  rule  to  fol- 
low  is :  Add  1  per  cent  of  salt  by  weight 
for  each  degree  Fahrenheit  below  32°  up 
to  a  máximum  of  10  per  cent. 

Calcium  Chloride  in  Mixing  Water. — It 

is  probable  that  the  best  all-around  results 
with  the  addition  of  calcium  chloride  are 
secured  when  the  addition  is  about  2  per 
cent  by  volume  of  the  mortar.  This  is 
substantially  a  15  to  20  per  cent  solution, 
the  freezing  point  of  which  is  14°  F.  to 
—  2o  F.  Richer  solutions  quicken  the  set  • 
of  the  cement  and  the  strength  of  the  mor- 
tar is  reduced  as  compared  with  the  2 
per  cent  solution. 

Heating  Concrete  Materials. — See  that 
concrete  materials — sand,  stone  and  water 
•—are  not  heated  to  excess.  Ordinarily 
the  heat  cannot  be  so  great  as  to  injure 
the  material  itself,  but  it  may  be  great 
enough  to  hasten  the  setting  of  the  cement 
so  much  as  to  cause  trouble  or  to  so  dry 
out  the   stone   that  it   will   absorb   enough 


6(5  CONCRETE    1NSPECTI0N. 

water  to  rob  the  cement  of  necessary  moist- 
ure  in  dry  mixtures. 

Frozen  Lumps  in  Concrete. — See  that 
lumps  of  frozen  sand  and  stone  do  not 
get  into  the  mixture  in  freezing  weather. 
The  use  of  hot  mixing  water  cannot  be 
depended  upon  always  to  thaw  such  lumps. 

Covering  the  Concrete. — See  that  the 
concrete  is  protected  f  rom  loss  of  heat  until 
set,  by  covering  it  so  as  to  prevent  radia- 
tion  of  the  heat.  Tar  paper  nailed  to  the 
outside  of  wall  form  studding  so  as  to 
form  a  dead  air  space,  coverings  of  hay 
or  straw  or  a  wood  covering  on  floors, 
etc.,  are  among  the  means  possible.  See 
that  manure  is  not  used;  it  keeps  the  con- 
crete warm,  but  it  also  stains  it  and  fre- 
quently  causes  disintegration. 

Artificial  Heaters. — See  that  the  con- 
crete and  the  forms  are  not  allowed  to  dry 
out  when  artificial  heaters  like  salamanders 
or  brick  ovens  are  used  to  keep  the  work 
warm.  Moisture  is  essential  to  the  proper 
setting  of  concrete,  and  the  loss  due  to 
cvaporation  from  concrete  and  forms  by 
dry  heat  must  be  replaced  by  sprinkling  or 
other  means. 

FINISHING   SURFACES. 

Special  surface  finishes  are  often  re- 
quired.  Specifications  should  be  particular 
and  explicit  regarding  the  character  and 
the  nicety  of  the  finish  required.  If  they 
are   not,   the   inspector   should   learn    from 


INSPBCTtON    OF    C0NCRET1NG.  67 

the  enginecr  the  quality  of  work  he  has 
in  mind  and  should  see  that  the  contractor 
clearly  understands  the  requirements.  Per- 
fection  of  finish  is  a  matter  of  attention 
and  skillful  workmanship,  and  the  inspector 
has  chiefly  to  watch  the  workmen.  Fin- 
ishes  are  of  two  classes :  (1)  Those  in 
which  the  molded  surface  is  treated  after 
the  forms  are  removed;  (2)  those  in  which 
the  molding  is  so  done  that  the  finish  is  a 
part  of  the  molding  process.  Faults  in 
finishes  of  the  second  class  must  be  pre- 
vented  during  molding  by  careful  work- 
manship,  for  after  the  concrete  has  once 
set  they  can  be  remedied  only  by  patch- 
ing,  which  is  unsatisfactory,  or  by  giving 
the  whole  surface  one  of  the  finishes  be- 
longing  in  the  first  class. 

Spaded  Finish. — See  that  the  coarse  ag- 
gregate  is  brotight  well  back  from  the  face 
and  that  the  fine  mortar  is  flushed  well 
against  the  forms.  Spading  is  best  done 
with  a  special  flat-bladed  spade,  having  the  ' 
blade  perforated  with  holes  or  slots,  which 
will  screen  back  the  stones  and  allow  the 
mortar  to  pass,  but  the  ordinary  spade  or 
shovel  can  be  used.  The  spade  is  shoved 
down  between  concrete  and  face  forms 
and  the  stones  are  pulled  away  from  the 
face. 

Spaded  and  Troweled  Finish. — See  that 
the  coarse  aggregate  is  well  pulled  back 
from  the  face  of  the  form  to  allow  the 
mortar  to   flush  to  the  surface.      See  that 


68 


CONCRETE    INSPECTION. 


the  forms  are  stripped  whilc  the  concrete 
is  still  green  enough  to  be  worked  down 
with  a  trowel. 

Mortar  Face  Finish. — See  that  the  fac- 
ing  mortar  and  the  concrete  backing  are 
placed  at  the  same  time  and  are  tamped 
together.  See  that  the  tamping  is  not  so 
hard  that  pieces  of  stone  are  forced 
through  the  facing  to  appear  on  the  sur- 
face,  but  that  it  is  hard  enough  to  bond 
thoroughly  the  facing  mortar  and  the  back- 
ing. 


Hcmctles 
fíiveied^ 
on  the  Fiare-. 


Fig.    12 — Facing   Form. 


The  preferable  method  of  construction 
is  to  use  a  facing  form  like  that  shown 
by  Fig.  12;  fill  between  the  facing  form 
and  the  lagging  with  mortar,  then  fill  be- 
hind  the  facing  form  with  the  backing, 
and  finally  withdraw  the  facing  form  and 
tamp  backing  and   facing  together. 

Dry  Concrete  Facing. — See  that  the  fac- 
ing   mixture   is    mixed*  so    dry    that    hard 


INSPECTION    OF    CONCRETING.  69 

tamping  will  not  flush  water  to  the  sur- 
face.  The  theory  of  dry  concrete  facing 
is  that  the  imprints  of  joints  and  other 
form  marks  are  not  readily  received  by  it. 
Froportions  of  1  part  cement,  3  parts 
screenings  and  3  parts  %-in.  crushed  stone 
have  proven  most  satisfactory. 

Grout  Washes. — See  that  holes  are  filled 
and  joint  marks  are  smoothed  down  be- 
fore  the  grout  wash  is  applied.  See  that 
the  grout  is  applied  in  a  thin  film.  If 
applied  with  a  brush  the  grout  should  have 
about  the  consisteney  of  ordinary  white- 
wash.  If  applied  with  a  trowel,  the  grout 
should  be  quite  stiff  and  applied  in  a  very 
thin  coat  and  troweled  or  rubbed  so  that 
only  the  pores  are  filled  and  no  body  of 
mortar  left  on  the  surface. 

Tooling  Concrete. — See  that  the  concrete 
has  aged  sufficiently  to  give  a  good,  clean 
tool  cut;  it  should  be  at  least  30  days  oíd, 
and  preferably  60  days  oíd.  The  amount 
and  character  of  the  tooling  will  be  deter- 
mined  by  the  specifications ;  ordinary  stone 
cutting  methods  are  employed. 

Scrubbed  Finish. — See  that  the  scrub- 
bing  continúes  just  long  enough  to  re- 
move  the  surface  cement  and  to  expose 
partially  the  sand  or  aggregate  without 
loosening  it.  See  that  the  cement  particles 
removed  by  the  brush  are  thoroughly 
flushed  off  the  surface  by  clean  water,  else 
they  will  adhere  in  patches  and  form  rough 
blotches. 


70  CONCRETE    INSPECTION. 

The  time  for  doing  the  scrubbing  is  when 
the  concrete  is  still  green,  but  is  firm 
enough  to  prevent  the  particles  of  sand  or 
stone  from  being  easily  torn  from  the  em- 
bedding  cement ;  this  time  varíes  with  the 
temperature,  the  wetness  of  the  mixture, 
the  activity  of  the  cement,  etc.,  and  is  a 
matter  of  judgment  for  each  particular 
case.  When  just  right  a  few  strokes  of 
an  ordinary  scrubbing  brush  with  plenty 
of  water  will  do  the  work. 

Acid  Wash  Finish. — See  that  the  acid 
wash  is  not  allowed  to  remain  too  long 
and  is  thoroughly  removed  by  washing 
with  clean  water.  The  acid  wash  should 
be  allowed  to  "work"  just  long  enough  to 
remove  the  surface  film  of  cement  and  to 
partly  expose  the  sand  grains  without  loos- 
cning  them.  Unless  the  surplus  acid  is 
all  removed  by  washing,  it  will  continué 
to  etch  out  the  cement  in  places  and  give 
a  pitted  and  blotched  surface. 

Gravel  or  Pebble  Finish. — Either  the 
scrubbing  or  the  acid  process  previously 
described  is  used  for  securing  gravel  or 
pebble  finish.  See  that  the  etching  or  scrub- 
bing process  is  continued  just  long  enough 
partly  to  expose  the  pebbles  without  loos- 
ening  them  in  their  cement  bed.  Under 
normal  weather  conditions  an  age  of  about 
24  hours  is  about  right  for  scrubbing; 
etching  with  acid  can  be  done  at  any  age. 

Plaster  Finish. — See  that  the  concrete 
surface  to  be  plastered  is  specially  treated 


1NSPECTI0N    OF    CONCREÍ  ING.  71 

to  receive  the  plaster  coat.  Plaster  will 
not  adhere  well  to  concrete  unless  the  sur- 
face  film  or  skin  is  removed,  or  at  least 
very  thoroughly  cleaned.  The  surface  skin 
may  be  removed  by  acid  washing,  scrub- 
bing  or  tooling.  Cleaning  must  be  done 
thoroughly.  McCullough*  gives  the  fol- 
lowing  directions :  "Clean  the  surface  with 
steam,  afterwards  using  wire  brushes  and 
then  the  steam  again.  Wet  with  water, 
paint  with  neat  cement  and  immediately 
follow  with  two  coats  of  one  to  three  mor- 
tar,  the  lower  coat  scratched  and  the  top 
coat  wood  floated  to  a  sand  surface." 

Painting  Concrete  Surfaces. — See  that 
the  concrete  is  perfectly  dry  and  that  its 
surface  is  prepared  to  receive  the  paint. 
This  direction  refers  to  painting  with  oil 
paints.  Special  paints  are  on  the  market 
for  concrete  which  are  claimed  not  to  re- 
quire  dry  or  specially  prepared  surfaces. 
When  these  paints  are  used  the  inspector 
must  follow  the  printed  directions  for  ap- 
plying  each.  The  following  method  of 
preparing  concrete  surfaces  to  receive  oil 
paints  has  been  found  successful:  Wash 
the  surface  thoroughly  with  a  7  to  8  per 
cent  solution  of  muriatic  acid  and  follow 
with  a  good  wash  of  clean  water.  After 
the  treated  surface  has  thoroughly  dried 
apply  the  paint,  using  enough  turpentine 
in  the  priming  coat  to  make  it  almost  fíat 

♦"Reinforced  Concrete,  A  Manual  of  Prac- 
tice,"    by  Ernest  McCullough. 


72  CONCRETE    1NSPECT10N. 

and  increasing  thc  amount  of  oil  each  suc- 
ceeding  coat.  Thc  concrete  should  have 
thoroughly  dried  out  before  painting  is  at- 
tempted. 


CHAPTER     VI.      INSPECTION     OF 
SIDEWALK   CONSTRUCTION. 

Cement  sidewalk  construction  is  a  task 
for  experienced  and  skillful  workmen 
which  is  often  undertaken  by  unskilled  and 
inexperienced  workmen.  Its  inspection  de- 
mands  cióse  attention  to  many  small  struc- 
turai  details  and  to  the  skill  and  honesty 
of  the  men  doing  the  work.  More  side- 
walks  by  far  fail  because  of  poor  work- 
manship  and  neglect  of  correct  principies 
of  construction  than  because  of  poor  ma- 
terials. 

Preparation  of  Foundation — See  that  the 
excavation  in  cut  reaches  to  firm  soil;  nev- 
er  permit  sub-base  to  be  laid  on  sod.  See 
that  soft,  spongy  spots,  roots  of  shrubs, 
etc.,  are  taken  out  and  the  cavities  filled 
with  firm  soil.  See  that  filis  are  of  ampie 
width  and  are  thoroughly  compacted.  If 
filis  are  narrow  they  wash  or  cave  down  so 
that  the  edge  of  the  sidewalk  slab  is  left 
overhanging  to  tip  or  break  down  under 
load. 

Material  for  Sub-Base.— See  that  the 
material  used  for  sub-base  is  of  such  a 
character  that  it  will  withstand  tamping 
without  crushing  to  an  extent  that  will 
prevent  proper  drainage. 

Compacting  Sub-Base. — See  that  the 
sub-base    is    thoroughly    compacted    by 


74  CONCRETE    INSPECTION. 

tamping  or   rolling;   see   that   the  top   is 
made  smooth  and  to  grade. 

Wetting  Sub-Base. — See  that  the  mate- 
rial of  the  sub-base  is  properly  wetted  be- 
fore  placing  base  concrete  on  it.  If  too 
dry  it  will  absorb  from  the  base  the  water 
necessary  for  the  perfect  hardening  of  the 
concrete. 

Material  for  Forms. — See  that  forms  are 
constructed  of  clean  lumber  not  less  than 
2  ins.  thick  and  5  or  6  ins.  wide.  See  that 
the  top  edges  of  the  boards  are  true;  they 
form  the  templets  for  striking  the  surface 
of  the  walk  to  grade. 

Alignment  and  Level  of  Forms. — See  that 
the  alignment  of  the  forms  is  exact  and 
that  their  level  conforms  to  the  finished 
grade.  The  top  edges  of  the  forms  serve 
as  templets  for  finishing  the  walk  and  they 
must  be  true  to  grade. 

Staking  of  Forms. — See  that  the  forms 
are  securely  staked  in  place;  the  side 
forms  by  stakes  abotit  2  ft.  apart  and  al- 
ternating  inside  and  outside,  the  cross 
forms  by  stakes  on  the  opposite  side  from 
that  on  which  the  concrete  is  being  de- 
posited. 

Spacing  of  Forms. — See  that  all  the 
forms  are  spaced  so  that  the  inside  meas- 
urements  are  exactly  those  of  the  "blocks" 
being  molded.  The  side  forms  should  be 
marked  to  show  where  joints  are  to  come 
and  the  cross  forms  should  be  placed  so 
that  the  face  against  which  the  concrete  is 


SIDEWALK    CONSTRUCTION.  75 

placed  is  in  line  with  the  marks  indicating 
positions  of  joints. 

Mixing. — See  that  the  concrete  is  thor- 
oughly  mixed  to  as  wet  a  consistency  as 
will  permit  thorough  tamping.  Mixing  is 
frequently  neglected  in  sidewalk  work  and 
it  must  be  watched.  See  that  excess  of  wa- 
ter is  not  used  to  get  the  plasticity  of  mix- 
ture that  should  be  got  by  thorough  mix- 
ing. 

Size  of  Batch  Mixed. — See  that  the  size 
of  batch  mixed  is  not  greater  in  amount 
than  the  quantity  that  can  be  placed, 
tamped  and  surfaced  before  initial  set  has 


frigr-Confr. 

Fig.  13 — Templet  for  Sidewalk  Work. 

commenced.  Usually  all  concrete  should  be 
deposited  within  40  minutes  from  time  of 
mixing.  Retempered  concrete  should  not  be 
used.  Any  concrete  left  over  at  quitting 
time  should  be  discarded. 

Placing  Base  Concrete. — See  that  as 
nearly  as  practicable  the  exact  amount  of 
concrete  is  deposited  which  when  tamped 
and  leveled  will  give  a  surface  below  the 
finished  surface  (the  top  edges  of  the 
forms)  just  the  depth  of  the  surface  finish. 
A  templet  of  the  general   form  shown  by 


76  CONCRETE    INSPECTION. 

Fig.  13  will  guarantee  the  proper  surface 
grade  of  the  base. 

Tamping  Base. — See  that  the  base  con- 
crete is  thoroughly  tamped.  The  concrete 
should  be  of  such  consistency  that  thor- 
ough  tamping  will  bring  just  a  film  of  wa- 
ter to  the  surface.  See  that  the  tamping  is 
as  thoroughly  done  at  edges  and  corners 
as  in  the  center  of  the  slab. 

Preserving  Joints  in  Base. — See  that  the 
joints  in  the  base  between  slabs  are  rigidly 
preserved. 


Fig#   14 — Sketch  Showing  Method  of  Concret- 
ing  Alternating  Slabs. 

(1).  After  the  slab  has  been  thoroughly 
tamped  remove  the  wood  cross-form  and 
stakes  so  as  to  preserve  the  vertical  face; 
tamp  the  concrete  of  the  next  base  block 
against  this  face. 

(2).  Use  a  thin  metal  cross-form  and 
leavé  it  in  place  until  both  slabs  are  com- 
pleted,  then  lift  it  out  vertically. 

(3).  Construct  alternating  slabs  inde- 
pendently  as  shown  by  Fig.  14.  After 
the  first  series  of  slabs,  1,  3,  5,  etc.,  has 
been  completed,  construct  the  second 
series,  2,  4,  6,  etc. 

Expansión  Joints. — See  that  expansión 
joints    are    constructed    as    specified.      The 


SIDEWALK    CONSTRUCTION.  77 

usual  practice  is  an  across-walk  expansión 
joint  at  approximately  cvery  50  ft.,  where 
new  walk  abutts  oíd  walk  (cement  or 
stone)  and,  where  new  walk  abutts  on  curb 
in  place.  A  recommended  construction  is  to 
replace  one  of  the  wooden  cross-forms  with 
a  metal  parting  strip  which  is  left  in  place 
until  the  walk  is  hard  and  is  then  removed 
and  the  crevice  filled  with  paver's  pitch. 

Method  of  Placing  Top  Mortar. — See 
that  the  method  of  placing  the  top  mortar 
is  one  which  is  -  recognized  to  guarantee 
successful  work  when  properly  carried  out. 
One  of  the  following  methods  is  common- 
ly  used : 

(1).  Mix  the  top  mortar  quite  thin, 
spread  it  regularly,  and  work  down  with 
a  straight-edge  until  the  surface  is  a  true 
plañe  flush  with  the  top  edges  of  the  forms. 

(2).  Mix  the  top  mortar  stiff;  spread  it 
evenly  and  somewhat  deeper  than  the  final 
surface  coat,  tamp  it  level  and  thoroughly 
into  the  base  concrete,  strike  concrete  with 
a  straight-edge  and  bring  low  spots  up  to 
grade. 

(3).  Use  a  base  concrete  rich  in  cement 
and  tamp  it  until  the  mortar  rises  to  the 
top  and  can  be  leveled  and  smoothed  by 
straight-edge  or  trowel. 

Consistency  of  Top  Mortar. — See  that 
top  mortar  to  be  placed  by  floating  under 
straight-edge  is  mixed  wet  enough  to 
"float"  readily.  If  too  stiff  it  cannot  be 
properly  worked  into  place,  and  if  too  thin 


78  CONCRETE    INSPECTION. 

it  takes  too  long  to  dry  out  ready  for  fin- 
ishing  and  is  Hable  to  result  in  sandy  spots. 
A  mushy  consistency  about  like  mortar  for 
brick  work  is  nearly  right.  See  that  top 
mortar  to  be  placed  by  tamping  is  dry 
enough  to  permit  thorough  tamping,  the 
tamping  should  bring  just  a  film  of  mois- 
ture  to  the  top. 

Time  of  Placing  Top  Mortar. — See  that 
the  top  mortar  is  placed  immediately  after 
the  base  is  tamped  into  position.  If  before 
placing  the  top  mortar  the  base  has  begun 
to  set  or  has  even  become  dry  or  has  had 
a  film  of  dust  or  dirt  blown  over  it,  the 
top  mortar  will  not  bond  with  the  base 
concrete  unless  special  precautions  are 
taken   in   placing  it. 

Bonding  Top  Mortar  to  Hardened  Base. 
— See  that  special  means  of  securing  bond 
are  employed  if  for  any  reason  the  top 
mortar  has  to  be  placed  on  base  concrete 
which  has  become  hard.  Two  methods  of 
bonding  with  success  are : 

(1).  Wash  the  top  surface  of  the  base 
concrete  thoroughly  with  water  and  brush 
off  all  dirt  and  loóse  material ;  apply  to  the 
washed  surface  a  thin  coat  of  cement  grout 
well  brushed  in;  apply  top  mortar  in  usual 
way  before  the  grout  has  dricd. 

(2).  Apply  an  acid  wash,  such  as  "Ran- 
somite,"  to  cut  the  surface  film  on  the 
concrete;  after  the  acid  wash  has  worked, 
wash  the  concrete  off  with  clean  water 
until    every   trace   of  acid   and   dirt   is   re 


SIDEIVALK    CONSTRUCTION.  70 

moved;  apply  the  top  mortar  to  the  wet 
surface  in  the  usual  way. 

Placing  top  mortar  on  hardened  base 
concrete  should  be  permitted  only  in  case 
of  absolute  necessity. 

Marking  Wearing  Coat. — See  that  the 
marking  of  the  wearing  coat  into  blocks  is 
directly  over  the  block  joints  in  the  base. 
This  rule  should  be  rigidly  enforced.  See 
that  the  marking  is  done  with  a  tool  which 
cuts  clear  through  to  the  base  and  that  the 
joint  is  finished  by  a  grooving  tool,  which 
leaves  a  rounded  edge. 

Finishing  Edges  of  Walk. — See  that  the 
edges  of  the  walk  are  finished  by  being 
rounded  off  to  a  curve  of  about  */2-in. 
radius.  A  spedal  tool  called  an  edger 
gives  the  best  finish. 

Protection  from  Frost. — Sidewalk  work 
should  not  be  done  in  freezing  weather  un- 
less  it  cannot  be  avoided.  If  construction 
in  freezing  weather  is  unavoidable  the  rules 
given  previously  for  concreting  in  freezing 
weather  should  be  followed. 

Protection  from  Rain. — See  that  the  fin- 
ished walk  is  protected  from  the  direct 
impact  of  rain  while  it  is  still  soft.  Rain 
falling  on  soft  mortar  washes  and  pits  the 
surface.  Any  covering  that  will  prevent 
the  direct  impact  and  wash  of  the  rain  on 
the  green  mortar  is  satisfactory. 

Protection  from  Sun. — See  that  the  walk 
is  protected  from  the  sun  until  thoroughly 
hardened.    Too  rapid   drying  weakens  the 


SO  CONCRETE    1NSPECTION. 

mortar  and  canses  hair  checking.  Too  rap- 
id  drying  by  warm  winds  must  also  be 
guarded  against. 

Various  methods  of  protecting  sidewalks 
from  too  rapid  drying  are  available.  One 
of  the  best  is  a  thick  covering  of  sand 
placed  directly  on  the  top  as  soon  as  it 
has  been  finished.  The  sand  conserves  the 
moisture  and  can  be  wet  down  if  more 
moisture  is  deemed  necessary.  Canvass,  tar 
paper,  boards,  etc.,  are  other  means  of  cov- 
ering that  may  be  adopted. 

Fractional  Slabs. — See  that  a  slab  is  not 
left  partly  completed  at  quitting  time.  The 
new  concrete  may  not  bond  with  the  oíd 
concrete  when  work  is  resumed  and  a  joint 
will  result.  In  no  case  should  the  base  be 
left  at  quitting  time  with  the  surface  fin- 
ish  unplaced.  The  entire  slab  should  be 
finished  complete  before  work  is  stopped. 


CHAPTER    VTT.      INSPECTTON     OF 

MOLDING     AND     DR1VING 

CONCRETE     PILES. 

Concrete  piles  are  constructed  by  tvvo 
methods:  (1)  A  hole  is  formed  in  the 
ground  by  driving  a  metal  pile  or  by  other 
means  and  is  filled  with  concrete;  (2)  a 
concrete  pile  is  cast  in  molds  and  after  it 
has  become  hard  is  driven  like  a  timber 
pile.  The  various  methods  of  molding 
piles  in  place  are  controlled  by  patents  and 
pile  construction  by  these  methods  is  done 
only  by  certain  firms.  Cast  piles  of  cer- 
tain  special  forms  are  also  patented,  but 
if  these  special  forms  be  excepted,  cast 
piles  may  be  made  and  driven  by  anyone. 
In  piles  molded  in  place  the  chief  uncer- 
tainties  are  whether  the  concrete  is  prop- 
erly  placed  and  tamped  and  remains  unin- 
jured  until  it  has  hardened  and  gained  its 
strength.  With  cast  piles  the  uncertainty 
is  whether  the  pile  after  driving  is  still 
sound  or  has  been  injured  by  the  driving.  * 
These  nncertain  points  are  the  chief  ones 
to  be  watched  out  for  by  the  inspector. 

Driving  Piles  in  Place. — See  that  the 
driving  of  shells  or  cores  for  new  piles 
does  not  injure  adjacent  piles  which  have 
been  concreted  but  in  which  the  concrete 
is  still  fresh  or  green.  The  jar  in  driving 
is  considerable  in  certain  kinds  of  ground 
and  may  readily  endanger  the  setting  and 
hardening     of     adjacent     concrete     work. 

81 


82  CONCRETE    1ÑSPECTJ0N. 

When  piles  are  cióse  driven  the  formation 
of  the  new  holes  may  also  so  compress  and 
shift  the  surrounding  soil  as  to  constrict  or 
distort  fresh  concrete  which  has  been 
placed  in  adjacent  holes  previously  formed. 

Constructing  Piles  in  Place. — See  that 
the  concrete  is  deposited  with  care  to 
prevent  seggregation  of  stone  from  mor- 
tar  and  to  prevent  admixture  of  dirt  with 
the  concrete.  A  strong,  dense  concrete  is 
needed  for  piles  and  the  usual  precautions 
for  securing  it  should  be  observed. 

Reinforcing  Piles  in  Place. — See  that  the 
reinforcement  is  set  parallel  and  concen- 
tric  with  the  axis  of  the  pile.  The  best 
practice  is  to  assemble  the  reinforcement 
into  a  unit  frame  and  to  place  it  as  a  unit. 

Cast  Piles. — See  that  cast  piles  are 
straight,  that  the  metal  points,  if  such  are 
used,  are  firmly  attached,  that  there  are  no 
cracks,  that  the  surface  is  not  deeply 
chipped  and  that  none  of  the  reinforcing 
metal  is  exposed.  If  cored  for  sinking 
by  water  jet  see  that  the  cores  are  open 
and  unobstructed ;  if  fluted  on  the  sides  to 
provide  passages  for  rise  of  water  used  in 
jetting  see  that  the  ñutes  or  corrugations 
are  not  obstructed. 

Molds  for  Cast  Piles.— See  that  the 
molds  are  constructed  straight  and  are  kept 
level  and  true  to  line.  Surface  roughness 
joint  marks,  etc.,  are  not  objectionable,  but 
a  pile  which  is  not  straight  is  Hable  to 
fracture    in    driving   or   under   load.       See 


MOLDING -.DRIVING   CONCRETE   PILES.    83 

that   the   molds   are   supported  by   a   rigid 
level  foundation  or  molding  bed. 

Reinforcing  Cast  Piles. — See  that  the  re- 
inforcement  is  set  parallel  to  and  concen- 
tric  with  the  axis  of  the  mold,  and  is  held 
rigidly  in  this  position  during  concreting. 
The  best  practice  is  to  assemble  and  wire 
the  reinforcement  into  unit  frames  for 
placing. 

Casting  Piles  in  Tiers. — See  that  inde- 
pendent  supports  are  provided  for  each 
tier  of  molds  in  casting  piles  in  tiers  to 
save  room. 

Concreting  Cast  Piles. — See  that  the  con- 
crete is  poured  at  several  points  along  the 
mold;  concrete  which  is  all  poured  at  one 
point  and  made  to  fill  the  mold  by  flowing 
is  likely  to  be  streaky. 

Driving  Cast  Piles. — See  that  the  driving 
of  cast  piles  is  so  done  that  the  pile  is  not 
fractured  in  the  body.  See  that  the  head 
is  protected  by  a  cushion  cap  to  take  the 
direct  blow  of  the  hammer.  Watch  the* 
driving  carefully  to  discover  cracks,  ex- 
cessive  spalling,  etc.  If  the  driving  is  done 
by  water  jet  see  that  the  pile  is  settled  to  a 
firm  bearing. 

Handling  Cast  Piles. — See  that  the  meth- 
od  of  handling  the  piles  to  the  driver  is 
such  that  damaging  strain  is  not  brought 
on  the  pile.  Cast  piles  may  be  cracked  by 
roughly  dragging  them  wjth  one  end  on 
the  ground  or  by  swinging  them  clear  by 
a  fastening  at  mid-length. 


CHAPTER    VIII.      INSPECTION    OF 
CAST   CONCRETE  WORK. 

Cast  concrete  work  comprises  hollow 
building  blocks,  lintles,  beams,  columns,  or 
other  molded  members,  and  ornamental 
shapes.  The  blocks,  etc.,  are  produced  by 
pouring,  tamping  or  compressing  concrete 
into  molds  and  permitting  it  to  harden  to 
the  molded  shape.  The  casting  or  mold- 
ing  is  commonly  done  in  factories  when 
the  inspection  relates  usually  to  the  fin- 
ished  block  alone,  bnt  sometimes  it  is  done 
on  the  work  when  the  inspection  relates  to 
methods  of  manufacture  as  well  as  to  the 
finished  product.  The  methods  of  mold- 
ing  and  hardening  are  so  many  that  only 
general  directions  for  inspection  can  be 
given;  for  special  variations  in  process  the 
inspector  must  devise  in  addition  rules  to 
fit  the  particular  characteristics  of  the 
work  in  hand. 

Methods  of  Molding. — Three  general 
processes  are  employed  for  molding  cast 
concrete  work:  (1)  A  dry  mixture  is 
heavily  tamped  into  a  mold  and  the  block 
is  immediately  released  and  sct  aside  for 
curing;  (2)  a  liquid  mixture  is  poured 
into  molds  where  the  blocks  remain  until 
hard;  (3)  a  médium  wet  mixture  is  com- 
pressed  into  molds  by  hydraulic  presses 
or  other  means  of  securing  great  pressure. 

84 


CAST    CONCRETE    WORK.  85 

Mixing  for  Dry  Mixture  Blocks. — See 

that  the  mixing  is  thorough  and  uniform. 
The  amount  of  water  used  for  dry  mix- 
ture blocks  is  so  small  that  it  can  be  even- 
ly  distributed  through  the  material  only  by 
careful  and  thorough  mixing. 

Consistency  of  Dry  Mixtures. — See  that 
the  mixture  is  as  wet  as  can  be  used  with- 
out  sticking  to  the  molds  and  without  sag- 
ging  or  sloughing  when  the  molds  are 
removed.  The  proper  consistency  has  to 
be  determined  by  experimenting  on  the 
materials  being  used.  The  block  should 
part  from  the  molds  without  sticking  and 
should  preserve  its  molded  form  perfectly. 

Size  of  Dry  Mixture  Batches. — See  that 
the  size  of  batch  mixed  is  not  greater  in 
amount  than  the  quantity  that  can  be 
molded  into  blocks  before  the  cement  be- 
gins  to  set. 

Molds  fcr  Dry  Mixture  Blocks. — See 
chat  the  molds  are  rigid  and  are  rigidly 
bolted,  clamped  or  locked  together.  Seé 
that  the  molds  are  so  constructed  that  they 
can  be  removed  or  "released"  without  in- 
jury  to  the  green  blocks.  See  that  the 
platens  or  working  plates  on  which  the 
block  is  carried  and  stacked  are  stiff 
enough  not  to  spring  under  the  load  and 
can  be  gotten  hold  of  for  carrying  with- 
out wrenching  or  tilting  the  green  block. 

Tamping  Dry  Mixtures. — See  that  the 
tamping  is  done  from  the  bottom  up  as 
the  mixture   is   filled   into  the  mold.     See 


86  CONCRETE    INSPECT10N. 

that  the  tamping  is  thorough,  that  the  ma- 
terial is  thoroughly  compacted  in  corners 
and  around  edges  as  well  as  in  the  center 
of  the  blocks.  Do  not  permit  the  mold  to 
be  half  filled  before  beginning  tamping, 
fill  the  mold  a  little  at  a  time  and  con- 
tinué tamping  from  the  first  shovelful  un- 
til  the  mold  is  filled.  Unless  the  tamping 
is  even  and  uniform  there  will  be  soft 
spots  in  the  block. 

Facing  Dry  Mixture  Blocks. — See  that 
the  facing  mixture  is  well  bonded  with 
the  concrete  backing  by  tamping  the  two 
together.  The  common  practice  is  to  place 
the  facing  mixture  against  the  bottom  or 
sides  of  the  mold  and  fill  above  or  be- 
hind  with  the  concrete  backing,  which  is 
tamped  as  the  filling  proceeds. 

Removing  Dry  Mixture  Blocks  From 
Molds. — See  that  the  block  is  removed 
from  the  mold  to  the  curing  skids  with- 
out  cracking  it  or  injuring  corners  or 
arrises.  A  dry  mixture  block  when  taken 
from  the  mold  has  no  cohesión  except  the 
tamping  density;  it  has  to  be  removed  and 
handled  with  great  care  to  prevent  in- 
jury.  Arrises  and  corners,  if  not  badly 
damaged,  can  be  repaired,  but  a  block 
which  is  cracked  cannot  be  satisfactorily 
repaired;  it  should  be  broken  up  and  the 
material  thrown  back  and  molded  over. 

Stacking  Dry  Mixture  Blocks. — See  that 
the  green  blocks  are  stacked  for  curing  in 
a   horizontal   position    on   unyielding   sup- 


CAST    CONCRETE    WORK.  87 

ports  and  so  as  not  to  touch  or  to  bring 
any   weight  on   adjacent  blocks. 

Protecting  Dry  Mixture  Blocks. — See 
that  blocks  are  molded  and  stored  for  cur- 
ing  so  that  they  cannot  be  acted  upon  by 
direct  rays  of  the  sun,  warm  air  currents 
or  frost.  A  shed  or  housing  should  be 
provided  for  both  molding  and  storing, 
and  the  molded  blocks  had  better  remain 
under  cover  for  at  least  a  week.  If  shed 
room  cannot  be  provided  for  a  week's  out- 
put  of  blocks,  the  blocks  may  be  carried 
outside  after  setting  and  covered  with  can- 
vas,  straw  or  other  covering  that  will 
preserve  the  moisture  and  shield  the  blocks 
from  the  sun  and  wind. 

Sprinkling  Dry  Mixture  Blocks. — See 
that  the  blocks  are  freely  supplied  with 
water  by  sprinkling.  A  dry  mixture  block 
does  not  have  enough  mixing  water  to  en- 
able  the  cement  to  set  and  harden  per- 
fectly  and  this  deficiency  has  to  be  sup- 
plied by  sprinkling.  The  sprinkling  should 
begin  as  soon  as  the  cement  is  hard 
enough  not  to  wash,  within  an  hour  af':er 
molding,  and  should  continué  for  at  least 
ten  days.  See  that  the  sprinkling,  particu- 
larly  while  the  block  is  still  soft,  is  done  by 
means  of  a  gentle  spray  which  will  not 
"wash"   the    concrete. 

Removing  Dry  Molded  Blocks  from 
Platens. — See  that  the  block  is  removed 
from  the  platen  by  up-ending  or  tipping  it 
onto  a  sand  cushion  and  that  the  platen  is 


88  CONCRETE    INSPECTION. 

loosened  by  tapping  it  lightly  and  not  by 
wrenching  or  prying.  Generally  the  platens 
are  removed  within  at  most  24  hours  and 
the  blocks  are  still  green  and  will  not  stand 
abuse. 

Curing  Period  for  Dry  Mixture  Blccks. 
— See  that  the  blocks  have  cured  for  at 
least  30  days  before  they  are  removed 
from  the  storage  yards  for  use  in  con- 
struction. 

fmddling  Wet  Mixtures. — See  that  the 
mixture  is  thoroughly  stirred  and  churned 
to  elimínate  air  voids,  prevent  arching  and 
íill  compactly  corners  and  edges  of  mold. 
The  mold  may  be  filled  in  one  pouring  if 
size  permits  and  if  two  or  more  batches 
are  required  for  filling  see  that  the  pouring 
is  as  nearly  continuous  as  practicable. 

Removing  Molds  from  Wet  Mixture 
Blocks. — See  that  the' mold  is  not  removed 
until  the  concrete  has  thoroughly  set  and 
is  strong  enough  to  do  without  the  sup- 
port  of  the  mold.  The  time  of  safe  re- 
moval  depends  on  the  nature  of  the  mold- 
ed  piece;  its  size,  shape,  weight  and  the 
strains  which  will  come  upon  it  in  the 
process  of  removing  the  forms.  A  small 
compact  block  can  be  turned  out  of  the 
molds  as  soon  as  the  cement  has  set  if 
care  is  used;  a  heavy  molded  girder  can 
have  the  sides  of  the  mold  removed  in  12 
to  24  hours  but  it  cannot  be  handled  for 
a  much  longer  period  depending  on  condi- 
tions. 


CAST    CONCRETE    WORK.  89 

Provisión  for  Handling  Molded    Blocks. 

— See  that,  in  molding  heavy  blocks,  suit- 
able  provisión  is  made  for  handling  by 
molding  dog  and  clevis  holes  in  the  block, 
inserting  pins  or  eye-bolts,  etc.  See  that 
these  holes  or  fastenings  are  liberal  in  size 
and  are  not  located  too  near  corners  or 
faces,  else  the  strain  of  lifting  will  shell  off 
the  concrete. 

Accuracy  of  Shape  and  Dimensions. — 
See  that  the ,  block  is  true  to  shape  and 
exact  in  dimensions,  with  faces  true  to 
plañe  and  edges  true  to  line.  See  that 
moldings  and  other  ornamentations  are 
perfect.  A  molded  block  should  be  equal 
in  perfection  to  cut  stone  in  all  particulars 
of  shape  and  dimensions. 


CHAPTER  IX.  STANDARD  AND 
TYPICAL  SPECIFICATIONS. 
Specifications  are  the  written  instruc- 
tions  defining  the  duties  of  the  inspector. 
He  should  be  familiar  with  their  charac- 
teristics  and  requirements  both  generally 
and  specifically.  A  study  of  specifica- 
tions is  essential  to  an  inspector  who  de- 
sires  to  keep  abreast  with  his  work.  It 
is  only  by  such  study  that  he  will  be 
able  to  interpret  their  requirements 
quickly,  accurately  and  fairly  on  any 
work  with  which  he  is  connected.  The 
following  specifications  are  given  here 
for  study.  They  are  not  selected  as  be- 
ing  ideal,  but  as  representing  general 
practice,  and  therefore  as  being  exempli- 
fications  of  what  the  inspector  may  ex- 
pect  to  find  his  business  to  interpret  and 
enforce  in  practical  work. 

SPECIFICATIONS    FOR    CEMENT.* 
General    Conditicns. 

1.  All  cement  shall  be  inspected. 

2.  Cement  may  be  inspected  either  at 
the  place  of  manufacture  or  on  the  work. 

3.  In  order  to  allow  ampie  time  for  in- 
specting  and  testing,  the  cement  should 


♦Standard  specifications  adopted  by  the 
American  Society  for  Testing  Materials,  Nov, 
14,   1904. 

90 


SPECIF1CA  TIONS.  9 1 

be  stored  in  a  suitable  weather-tight 
building  having  the  floor  properly 
blocked  or  raised  from  the  ground. 

4.  The  cement  shall  be  stored  in  such  a 
manner  as  to  permit  easy  access  for 
proper  inspection  and  identification  of 
each  shipment. 

5.  Every  facility  shall  be  provided  by 
the  contractor  and  a  period  of  at  least 
12  days  allowed  for  the  inspection  and 
necessary  tests. 

6.  Cement  shall  be  delivered  in  suitable 
packages  with  the  brand  and  ñame  of 
manufacturer  plainly  marked  thereon. 

7.  A  bag  of  cement  shall  contain  94 
lbs.  of  cement  net.  Each  barrel  of  Port- 
land  cement  shall  contain  4  bags,  and 
each  barrel  of  natural  cement  shall  con- 
tain 3  bags  of  the  above  net  weight. 

8.  Cement  failing  to  meet  the  7-day 
requirements  may  be  held  awaiting  the 
results  of  the  28-day  tests  before  rejec- 
tion. 

9.  All  tests  shall  be  made  in  accord- 
anee  with  the  methods  proposed  by  the 
Committee  on  Uniform  Tests  of  Cement 
of  the  American  Society  of  Civil  Engi- 
neers,  presented  to  the  society  January 
21,  1903,  and  amended  January  20,  1904, 
with  all  subsequent  amendments  thereto. 

10.  The  acceptance  or  rejection  shall 
be  based  on  the  following  requirements: 

Natural  Cement. 

11.  Definition. — This  term  will  be  ap- 


92  CONCRETE    1NSPECTI0N. 

plied  to  the  finely  pulverized  product  re- 
sulting  from  the  calcination  of  an  argil- 
laceous  limestone  at  a  temperature  only 
sufficient  to  drive  oí¥  the  carbonic  acid 
gas. 

12.  Specific  Gravity. — The  specific 
gravity  of  the  cement  thoroughly  dried 
at  100°  C.  shall  be  not  less  than  2.8. 

13.  Fineness. — It  shall  leave  by  weight 
a  residue  of  not  more  than  10  per  cent 
on  the  No.  100  and  30  per  cent  on  the 
No.  200  sieve. 

14.  Time  of  Setting. — It  shall  develop 
initial  set  in  not  less  than  10  minutes  and 
hard  set  in  not  less  than  30  minutes,  ñor 
more  than  3  hours. 

15.  Tensile  Strength. — The  minimum 
requirements  for  tensile  strength  for 
briquettes  1  in.  square  in  cross  section 
shall  be  within  the  following  limits  and 
shall  show  no  retrogression  in  strength 
within  the  periods  specified:* 

Strength. 
Age.  Neat   Cement.  Lbs. 

24  hours  in  moist  air 50-100 

7  days  (1  day  in  moist  air,  6  days  in 

water)    100-200 

28  days  (1  day  in  moist  air,  27  days  in 

water)    200-300 

One  Part  Cement,  Three  Parts 
Standard   Sand. 
7  days  (1  day  in  moist  air,  6  days  in 

water)    25-  75 

28  days  (1  day  in  moist  air,  27  days  in 

water)    75-150 

♦For  example,  the  minimum  requirement 
for  the  24-hour  neat  cement  test  should  be 
some  specified  valué  within  the  limits  of  50 
and  100  lbs.,  and  so  on  for  each  period  stated. 


SPECIFICATIONS.  93 

16.  Constancy  of  Volume. — Pats  of 
neat  cement  about  3  ins.  in  diameter,  V2 
in.  thick  at  center,  tapering  to  a  thin 
edge,  shall  be  kept  in  moist  air  for  a 
period  of  24  hours. 

(a)  A  pat  is  then  kept  in  air  at  nor- 
mal temperature. 

(b)  Another  is  kept  in  water  main- 
tained  as  near  70°  F.  as  practicable. 

17.  These  pats  are  observed  at  inter- 
vals  for  at  least  28  days,  and,  to  satisfac- 
torily  pass  the  tests,  should  remain  firm 
andhard  and  show  no  signs  of  distor- 
tion,  checking,  cracking  or  disintegrat- 
ing. 

Portland  Cement. 

18.  Definition. — This  term  is  applied  to 
the  finely  pulverized  product  resulting 
from  the  calcination  to  incipient  fusión 
of  an  intímate  mixture  of  properly  pro- 
portioned  argillaceous  and  calcareous 
materials,  and  to  which  no  addition 
greater  than  3  per  cent  has  been  made 
subsequent  to  calcination. 

19.  Specific  Gravity. — The  specific 
gravity  of  the  cement,  thoroughly  dried 
at  100°  C,  shall  be  not  less  than  3.10. 

20.  Fineness. — It  shall  leave  by  weight 
a  residue  of  not  more  than  8  per  cent  on 
the  No.  100,  and  not  more  than  25  per 
cent  on  the  No.  200  sieve. 

21.  Time  of  Setting. — It  shall  develop 
initial   set   in   not   less   than  30  minutes, 


94  CONCRETE    INSPECT10N. 

but   must   develop    hard    set   in   not    less 
than  1  hour,  ñor  more  than  10  hours. 

22.  Tensile  Strength. — The  mínimum 
requirements  for  tensile  strength  for  bri- 
quettes  1  in.  square  in  section  shall  be 
within  the  following  limits,  and  shall 
show  no  retrogression  in  strength  with- 
in the  periods  specified:* 

Strength. 
Age.  Neat   Cement.  Lbs. 

24  hours   in   moist   air 150-200 

7  days  (1  day  in  moist  air,  6  days  in 

water)    450-550 

28  days  (1  day  in  moist  air,  27  days  in 

water)    550-650 

One  Part  Cement,  Three  Parts  Sand. 
7  days  (1  day  in  moist  air,  6  days  in 

water)    150-200 

28  days  (1  day  in  moist  air,  27  days  in 

water)    200-300 

23.  Constancy  of  Volume. — Pats  of 
neat  cement  about  3  ins.  in  diameter,  V2 
in.  thick  at  the  center,  and  tapering  to  a 
thin  edge,  shall  be  kept  in  moist  air  for  a 
period  of  24  hours. 

(a)  A  pat  is  then  kept  in  air  at  normal 
temperature  and  observed  at  intervals 
for  at  least  28  days. 

(b)  Another  pat  is  kept  in  water  main- 
tained  as  near  70°  F.  as  practicable,  and 
observed  at  intervals  for  at  least  28 
days. 

(Y)  A  third  pat  is  exposed  in  any  con- 
venient  way  in  an  atmosphere  of  steam, 

*For  example,  the  mínimum  requirement 
for  the  24-hour  neat  cement  test  should  be 
some  specified  valué  within  the  limits  of  15C 
and  200  lbs.,  and  so  on  for  each  period  stated. 


SPEC1P1CATI0NS.  95 

above  boiling  water,  in  a  loosely  closed 
vessel  for  5  hours. 

24.  These  pats,  to  satisfactorily  pass 
the  requirements,  shall  remain  firm  and 
hard  and  show  no  signs  of  distortion, 
checking,  cracking  or  disintegrating. 

25.  Sulphuric  Acid  and  Magnesia. — 
The  cement  shall  not  contain  more  than 
1.75  per  cent  of  anhydrous  sulphuric  acid 
(S03),  ñor  more  than  4  per  cent  of 
magnesia  (MgO). 

SPECIFICATIONS  FOR  PORTLAND 

CEMENT  CONCRETE  AND  RE- 

INFORCED    CONCRETE.* 

1.  Cement  shall  be  Portland  and  shall 
meet  the  requirements  of  the  standard 
specifications. 

2.  Fine  aggregate  shall  consist  of  sand, 
crushed  stone,  or  gravel  screenings 
graded  from  fine  to  coarse  and  passing 
when  dry  a  screen  having  ^-in.  diameter 
holes;  it  shall  preferably  be  of  siliceous 
material,  clean,  coarse,  free  from  vegeta- 
able    loam    or    other    deleterious    matter, 

.  and  not  more  than  6  per  cent  shall  pass 
a  sieve  having  100  meshes  per  linear 
inch. 

3.  Mortars  composed  of  one  part  Port- 
land cement  and  three  parts  fine  aggre- 
gate   by    weight    when    made    into    bri- 

*Adopted  by  the  American  Railway  En- 
gineering  and  Maintenance  of  Way  Asso- 
ciation. 


96  CONCRETE    INSPECTION. 

quettes  shall  show  a  tensile  strength  of 
at  least  70  per  cent  of  the  strength  of 
1 — 3  mortar  of  the  same  consistency 
made  with  the  same  cement  and  stand- 
ard Ottawa  sand. 

4.  Coarse  aggregate  shall  consist  of 
crushed  stone  or  gravel,  graded  in  size, 
and  which  is  retained  on  a  screen  hav- 
ing  54_m-  diameter  holes;  it  shall  be 
clean,  hard,  durable  and  free  from  all 
deleterious  material.  Aggregates  con- 
taining  soft,  fíat  or  elongated  partióles 
shall  not  be  used. 

5.  The  máximum  size  of  the  coarse 
aggregate  shall  be  such  that  it  will  not 
sepárate  from  the  mortar  in  laying  and 
will  not  prevent  the  concrete  fully  sur- 
rounding  the  reinforcement  or  filling  all 
parts  of  the  forms.  Where  concrete  is 
used  in  mass  the  máximum  size  of  the 
coarse  aggregate  may,  at  the  option  of 
the  engineer,  be  such  as  to  pass  a  3-in. 
ring.  For  reinforced  concrete,  sizes 
usually  are  not  to  exceed  one  inch  in 
any  direction,  but  may  be  varied  to  suit 
the  character  of  the  reinforcement. 

6.  The  water  used  in  mixing  concrete 
shall  be  free  from  oil,  acid,  alkalies  or 
vegetable  matter. 

7.  The  metal  reinforcement  steel  shall 
be  manufactured  from  new  billets,  and 
shall  meet  the  requirements  of  the  fol- 
lowing  specifications,  and  be  free  from 
rust,  scale  or  coatings  of  any  character 


SPECIFICA  TIONS. 


97 


which  would  tend  to  reduce  or  destroy 

the  bond. 

Specifications    for    Steel    Reinforcement. 

8.  Steel  shall  be  made  by  the  open 
hearth  process. 

9.  The  chemical  and  physical  proper- 
ties  shall  conform  to  the  following 
limits: 


Elemer»ts  Considered. 

Structural 
Steel. 

High  Car- 
bón Steel. 

Phosphorus,  max.  1  AcfdC 
Sulphur,  máximum 

0.04% 
0.06% 
0.05% 

0.085% 
0.075% 

Ultímate  tensile  strength. 

Pounds  per  square  inch 

( 

Desired. 

60.000 
1,500,000* 

Desired. 
85.000Í 
1,400,000 

Elong.,  min.  %  in  8" j 

"2" 

Ult.tensi1e 

strength 

22 

Silky 

180°  flatt 

Ult.  tensile 
strength 

Character  of  fracture 

Cold  bends  without  fracture .  . 

180°  'd='Ú' 

*See  paragraph  16. 
JSee  paragraph  20. 


tSee  paragraphs  17,  18  and  19. 


10.  The  yield  point,  as  indicated  by  the* 
drop  of  beam,  shall  be  not  less  than  60 
per  cent  of  the  ultímate. 

11.  If  the  ultímate  strength  varíes  more 
than  4,000  lbs.  from  that  desired,  a  re- 
test shall  be  made  on  the  same  gage, 
which,  to  be  acceptable,  shall  be  within 
5,000  lbs.  of  the  desired  ultímate. 

12.  Chemical  determinations  of  the 
percentages  of  carbón,  phosphorus,  sul- 
phur and  manganese  shall  be  made  by 
the  manufacturer  from  a  test  ingot  taken 


98  CONCRETE   1NSPECTI0N. 

at  the  time  of  the  pouring  of  each  melt 
of  steel,  and  a  correct  copy  of  such 
analysis  shall  be  furnished  to  the  engi- 
neer  or  his  inspector.  Check  analyses 
shall  be  made  from  finished  material,  if 
called  for  by  the  purchaser,  in  which 
case  an  excess  of  25  per  cent  above  the 
required  limits  will  be  allowed. 

13.  Plates,  Shapes  and  Bars. — Speci- 
mens  for  tensile  and  bending  tests  for 
shapes  and  bars  shall  be  made  by  cutting 


About  l*   ♦    __Parallel  Section 


Not  less  than  o"     „ 

fe- 


Abóut  2n 


About  18"- 


Fig.    15 — Test  Piece   for   Testing   Reinforcing 
Steel. 

coupons  from  the  finished  product,  which 
shall  have  both  faces  rolled  and  both 
edges  milled  to  the  form  shown  by  Fig. 
15,  or  with  both  edges  parallel,  or  they 
may  be  turned  to  a  diameter  of  }i  in. 
with  enlarged  ends. 

14.  Bars  shall  be  tested  as  rolled. 

15.  At  least  one  tensile  and  one  bend- 
ing test  shall  be  made  from  each  melt  of 
steel  as  rolled. 

16.  For  material  less  than  5/16  in.  and 
more  than  Va  in.  in  thickness  the  follow- 


SPEC1FICA  T10NS.  93 

ing  modifications  will  be  allowed  in  the 
requirements  for  elongation: 

(a)  For  each  1/16  in.  in  thickness  be- 
low  5/16  in.,  a  deduction  of  2y2  will  be 
allowed  from  the  specified  percentage. 

(b)  For  each  %  in.  in  thickness  above 
¿4  in.,  a  deduction  of  1  will  be  allowed 
from  the  specified  percentage. 

17.  Bending  tests  may  be  made  by 
pressure  or  by  blows.  Shapes  and  bars 
less  than  one  inch  thick  shall  bend  as 
called  for  in  paragraph  9. 

18.  Structural  steel  one  inch  thick  and 
over,  tested  as  rolled,  shall  bend  cold  180 
degrees  around  a  pin,  the  diameter  of 
which  is  equal  to  twice  the  thickness  of 
the  bar,  without  fracture  on  the  outside 
of  bend. 

19.  Finished    material     shall     be     free 
from   injurious  seams,  flaws,   cracks,  de- 
fective  edges  or  other  defects,  and  have 
a  smooth,  uniform  and  workmanlike  fin-, 
ish. 

20.  Every  finished  piece  of  steel  shall 
have  the  melt  number  and  the  ñame  of 
the  manufacturer  stamped  or  rolled  upon 
it,  except  that  bar  steel  and  other  small 
parts  may  be  bnndled  with  the  above 
marks  on  an  attached  metal  tag. 

21.  Material  which,  subsequent  to  the 
above  tests  at  the  milis,  and  its  accept- 
ance  there,  develops  weak  spots,  brittle- 
ness,  cracks  or  other  imperfections,  or  is 
found  to  have  injurious  defects,  will  be 


100  CONCRETE    1NSPECTION. 

rejected  at  the  shop  and  shall  be  re- 
placed  by  the  manufacturer  at  his  own 
cost. 

Preparation  and  Placing  of  Mortar  and 
Concrete. 

22.  The  materials  to  be  used  in  con- 
crete shall  be  of  uniform  quality  and  so 
proportioned  as  to  secure  as  nearly  as 
possible  a  máximum  density. 

23.  The  unit  of  measure  shall  be  the 
barrel,  which  shall  be  taken  as  contain- 
ing  3.8  cubic  feet.  Four  bags  containing 
94  lbs.  of  cement  each  shall  be  consid- 
ered  the  equivalent  of  one  barrel.  Fine 
and  coarse  aggregate  shall  be  measured 
separately  as  loosely  thrown  into  the 
measuring  receptacle. 

24.  The  fine  and  coarse  aggregate  shall 
be  used  in  such  relative  proportions  as 
will  insure  máximum  density. 

25.  For  reinforced  concrete  construc- 
tion  a  density  proportion  based  on  1:6 
shall  be  used;  i.  e.,  one  part  of  cement  to 
a  total  of  six  parts  of  fine  and  coarse  ag- 
gregates  measured  separately. 

26.  For  massive  masonry  or  rubble 
concrete  a  density  proportion  based  on 
1:9  shall  be  used. 

27.  The  ingredients  of  concrete  shall 
be  thoroughly  mixed  to  the  desired  con- 
sistency,  and  the  mixing  shall  continué 
until  J;he  cement  is  uniformly  distributed 


SPEC1FICATI0NS.  101 

and   the   mass   is    uniform    in    color   and 
homogeneous. 

28.  Methods  of  measurement  of  the 
proportions  of  the  various  ingredients, 
including  the  water,  shall  be  used,  which 
will  secure  sepárate  uniform  measure- 
ments  at  all  times. 

29.  When  the  conditions  will  permit,  a 
batch  mixer  of  a  type  which  insures  uni- 
form mixing  of  the  materials  throughout 
the  mass  shall  be  used. 

30.  When  it  is  necessary  to  mix  by 
hand,  the  mixing  shall  be  on  a  water- 
tight  platform  and  especial  precautions 
shall  be  taken  to  turn  the  materials  until 
they  are  homogeneous  in  appearance 
and  color. 

a.  Tight  platforms  shall  be  provided  of 
sufficient  size  to  accommodate  men  and 
materials  for  the  progressive  and  rapid 
mixing  of  at  least  two  batches  of  con- 
crete at  the  same  time.  Batches  shall» 
not  exceed  one  cubic  yard  each,  and 
smaller  batches  are  preferable,  based 
upon  a  múltiple  of  the  number  of  sacks 
of  cement  to  the  barrel. 

b.  Spread  the  fine  aggregates  evenly 
upon  the  platform,  then  the  cement  upon 
the  fine  aggregates,  and  mix  thoroughly 
until  of  an  even  color.  Add  all  the  water 
necessary  to  make  a  thin  mortar  and 
spread  again;  add  the  coarse  aggregates, 
which,  if  dry,  should  first  be  thoroughly 


102  CONCRETE    INSPECTION. 

wet  down.  Turn  the  mass  with  shovels 
or  hoes  until  thoroughly  incorporated 
and  all  the  aggregates  are  covered  with 
mortar;  this  will  probably  require  the 
mass  to  be  turned  four  times. 

c.  Another  approved  method,  which 
may  be  permitted  at  the  option  of  the 
engineer  in  charge,  is  to  spread  the  fine 
aggregates,  then  the  cement,  and  mix 
dry,  then  the  coarse  aggregates;  add  wa- 
ter and  mix  thoroughly  as  above. 

31.  The  materials  shall  be  mixed  wet 
enough  to  produce  a  concrete  of  such  a 
consistency  as  will  flow  into  the  forms 
and  about  the  metal  reinforcement  and 
which,  on  the  other  hand,  can  be  con- 
veyed  from  the  place  of  mixing  to  the 
forms  without  separation  of  the  coarse 
aggregate  from  the  mortar. 

32.  Retempering  mortar  or  concrete — - 
i.  e.,  remixing  with  water  after  it  has 
partially  set — shall  not  be  permitted. 

33.  Concrete  after  the  addition  of  wa-. 
ter  to  the  mix  shall  be  handled  rapidly 
from  the  place  of  mixing  to  the  place  cf 
final  deposit,  and  under  no  circumstances 
shall  concrete  be  used  that  has  partially 
set  before  final  placing. 

34.  The  concrete  shall  be  deposited  in 
such  a  manner  as  will  permit  the  most 
thorough  compacting,  such  as  can  be  ob- 
tained  by  working  with  a  straighí  shovel 
or  slicing  tool  kept  moving  up  and  down 


SPECIFICA  TIONS.  103 

until  all  the  ingredients  have  settled  in 
their  proper  place  by  gravity  and  the 
surplus  water  forced  to  the  surface. 

35.  In  depositing  the  concrete  under 
water,  special  care  shall  be  exercised  to 
prevent  the  cement  from  floating  away, 
and  to  prevent  the  formation  of  laitance. 

36.  Before  placing  the  concrete  the 
forms  shall  be  thoroughly  wetted  and 
the  space  to  be  occupied  by  the  concrete 
free  from  debris. 

37.  When  work  is  resumed,  concrete 
previously  placed  shall  be  roughened, 
thoroughly  cleansed  of  foreign  material 
and  laitance,  drenched  and  slushed  with 
a  mortar  consisting  of  one  part  Portland 
cement  and  not  more  than  two  parts  fine 
aggregate. 

38.  The  faces  of  concrete  exposed  to 
premature  drying  shall  be  kept  wet  for  a 
period  of  at  least  seven  days. 

39.  The  concrete  shall  not  be  mixed  or  • 
deposited  at  a  freezing  temperature,  un- 
less  special  precautions,  aproved  by  the 
engineer,  are  taken  to  avoid  the  use  of 
materials  containing  frost  or  covered 
with  ice  crystals,  and  to  provide  means 
to  prevent  the  concrete  from  freezing 
after  being  placed  in  position  and  until  it 
has  thoroughly  hardened. 

40.  Where  the  concrete  is  to  be  de- 
posited in  massive  work,  clean  stones 
thoroughly  embedded  in  the  concrete  as 


104  CONCRETE    INSPECT10N. 

near  together  as  is  possible  and  still  en 
tirely    surrounded    by    concrete    may    be 
used  at  the  option  of  the  engineer. 

41.  Forms  shall  be  substantial  and  un- 
yielding  and  built  so  that  the  concrete 
shall  conform  to  the  designed  dimen- 
sions  and  contours,  and  so  constructed 
that  the  leakage  of  mortar  is  prevented. 

42.  The  forms  shall  not  be  removed 
until  authorized  by  the  engineer. 

43.  For  all  important  work,  the  lumber 
used  for  face  work  shall  be  dressed  to  a 
uniform  thickness  and  width,  and  shall 
be  sound  and  free  from  loóse  knots,  se- 
cured  to  the  studding  or  uprights  in 
horizontal  lines. 

44.  For  backings  and  other  rough 
work  undressed  lumber  may  be  used. 

45.  Where  corners  of  the  masonry  and 
other  projections  Hable  to  injury  occur, 
suitable  moldings  shall  be  placed  in  the 
angles  of  the  forms  to  round  or  bevel 
them  off. 

46.  Lumber  once  used  in  forms  shall 
be  cleaned  before  being  used  again. 

47.  In  dry  but  not  freezing  weather  the 
forms  shall  be  drenched  with  water  be- 
fore the  concrete  is  placed  against  them. 

Details    of    Construction. 

48.  Wherever  it  is  necessary  to  splice 
the  reinforcement  by  lapping,  the  length 
of  lap  will  be  decided  by  the  engineer  on 
the  basis  of  the  safe  bond  stress  and  the 


SPECIFICA  TIONS.  105 

stress  in  the  reinforcement  at  the  point 
of  splice.  Splices  shall  not  be  made  at 
points  of  máximum  stress. 

49.  Concrete  structures,  wherever  pos- 
sible,  shall  be  cast  at  one  operation,  but 
when  this  is  not  possible  the  work  shall 
be  stopped,  so  that  the  resulting  joint 
will  have  the  least  effect  on  the  strength 
of  the  structure. 

50.  Girders  and  slabs  shall  not  be  con- 
structed  over  freshly  formed  wall  or  col- 
umns  without  permitting  a  period  of  at 
least  two  hours  to  elapse  to  provide  for 
settlement  or  shrinkagc  in  the  supports. 
Before  resnming  work  the  top  of  the 
supports  should  be  thoroughly  cleansed 
of  foreign  matter  and  laitance. 

51.  In  massive  work,  such  as  retaining 
walls,  abutments,  etc.,  built  without  rein- 
forcement, joints  shall  be  provided,  ap- 
proximately,  every  50  feet  throughout 
the  length  of  the  structure  to  take  care 
of  temperature  changes.  To  provide 
against  the  structures  being  thrown  out 
of  line  by  unequal  settlement,  each  sec- 
tion  of  the  wall  may  be  tongued  and 
grooved  into  the  adjoining  section.  To 
provide  against  unsightly- cracks,  due  to 
unequal  settlement,  a  joint  shall  be  made 
at  sharp  angles. 

52.  The  desired  finish  of  the  surface 
shall  be  determined  by  the  engineer  be- 
fore the  concrete  is  placed,  and  the  work 
shall  be  so  conducted  as  to  make  it  pos- 


100  CONCRETE    INSPECTION. 

sible  to  secure  the  finish  desired.     Plas- 
tering  of  surface  will  not  be  permitted. 

SPECIFICATIONS        FOR        MATE- 
RIALS AND  WORKMANSHIP 
FOR  BUILDING  CON- 
STRUCTION.* 

Quality  of  Materials. 

Portland  cement  shall  conform  to  the 
requirements  of  the  specifications  of  the 
American  Society  for  Testing  Materials, 
as  adopted  June  14,  1904,  with  all  subse- 
quent  amendments  thereto. 

Aggregates. — Fine  aggregates  shall  be 
well  graded  in  size  from  the  finest  to  at 
least  the  size  retained  on  a  No.  10  sieve. 
Coarse  aggregates  shall  also  be  well 
graded  in  size  from  the  finest  to  at  least 
the  size  retained  by  a  9/16-in.  ring.  Fine 
aggregates  may  contain  not  more  than  5 
per  cent,  by  weight,  of  clay,  but  no  other 
impurities.  Coarse  aggregates  shall  con- 
tain no  impurities. 

Sand  shall  be  equal  in  quality  to  the 
Mississippi  River  sand. 

Broken  stone  shall  be  either  limestone, 
chatts,  or  granite,  or  some  other  stone 
equal  to  one  of  these  in  the  opinión  cf 
the  commissioner  of  public  buildings. 

Hard  burned  clay  shall  be  made  from 
suitable    clay    free    from     sand    or    silt. 


*Extracts   from  the  Building  Ordinance  of 
the  City  of  St.  Louis,  Mo. 


SPECIFICATIONS.  107 

burned  hard  and  thoroughly.  Absorp- 
tion  of  water  should  not  exceed  15  per 
cent. 

Concrete. — The  solid  ingredients  of  the 
concrete  shall  be  mixed  by  volume  in 
one  of  the  following  proportions: 

(a)  Not  more  than  3  parts  fine  aggre- 
gate  to  1  of  cement. 

(b)  Not  more  than  2  parts  of  fine  ag- 
gregate  and  4  parts  of  coarse  aggregate 
to  1  of  cement;  but  in  all  cases  the  fine 
aggregate  shall  be  50  per  cent  of  the 
coarse  aggregate. 

Concrete  shall  have  an  ultímate 
strength  in  compression  in  28  days  of 
not  less  than  the  following: 

Burned  clay  concrete,  1,000  lbs.  per  sq. 
in. 

All  other  concrete,  2,000  lbs.  per  sq.  in. 

Steel  shall  be  médium  steel  or  high 
elastic  limit  steel.  The  physical  proper- 
ties  shall  conform  to  the  following  lim- 
its: 

Médium  H;gh  Elastic 

Steel.  Limit  Steel. 

T?u„+;„  i;«,;*  /    Not  less  than      Not  less  than 

blastic  hmit |  30^00  mm 

Percentage  of  elon-]         1,800,000    tA  „     1,800,000    1A 

fns  .n,.min;.ln  8r"Fió56o"10  £=Fío^ooo-10 

Coldbend  wi'thout)  qrt°  tn  radium- 

£e?crm%r°enncrer           "^  SUoTfess 

Character  of  frac-1            q.-iw  Silky  or  fine 

ture /            oiiKy  granular 

/  =  unit  stress  in  steel  at  rup tures. 

Tests  shall  be  made  on  specimens  tak- 
en    from    the    finished   bar,   and   certified 


108  CONCRETE    1NSPECTION. 

copies  of  test  reports  shall  be  furnished 
the  commissioner  of  public  buildings. 

Bending  tests  shall  be  made  by  pres- 
sure. 

Finished  material  shall  be  free  from 
seams,  flaws,  cracks,  defective  edges  or 
other  defects,  and  have  a  smooth,  uni- 
form  and  workmanlike  finish,  and  shall 
be  free  from  irregularities  of  all  kinds. 

The  net  área  of  cross  section  of  fin- 
ished steel  members  shall  not  be  less 
than  95  per  cent  of  the  área  shown  in  the 
approved  design. 

Execution. 

All  reinforced  concrete  work  shall  be 
built  in  accordance  with  approved  de- 
tailed  working  drawings.  These  draw- 
ings  shall  be  submitted  to  the  Commis- 
sioner of  Public  Buildings  for  approval 
and  no  work  shall  be  commenced  until 
the  drawings  shall  have  been  approved 
by  him. 

The  steel  used  for  reinforcing  concrete 
shall  havé  no  paint  upon  it,  but  shall  pre- 
sent  only  a  clean  or  slightly  rusted  sur- 
face  to  the  concrete.  All  dirt,  mud  and 
other  foreign  matter  shall  be  removed. 

If  the  steel  has  more  than  a  thin  film 
of  rust  upon  its  surface  it  shall  be 
cleaned  before  placing  in  the  work. 

In  proportioning  materials  for  con- 
crete, one  bag  containing  not  less  than 
93  lbs.  of  cement  shall  be  considered  1 
cu.  ft. 


SPECIFICATIONS.  109 

The  ingredients  of  the  concrete  shall 
be  so  thoroughly  mixed  that  the  cement 
shall  be  uniformly  distributed  through- 
out  the  mass  and  that  the  resulting  con- 
crete will  be  homogeneous. 

The  concrete  shall  be  mixed  as  wet  as 
possible  without  causing  a  separation  of 
the  cement  from  the  mixture,  and  shall 
be  deposited  in  the  work  in  such  manner 
as  not  to  cause  the  separation  of  mortar 
from  coarse  aggregate. 

Concrete  shall  be  placed  in  the  forms 
as  soon  as  practicable  after  mixing,  and 
in  no  case  shall  concrete  be  used  if  more 
than  1  hour  has  elapsed  since  the  addi- 
tion  of  its  water.  It  shall  be  deposited 
in  horizontal  layers  not  exceeding  8  ins. 
in  thickness  and  thoroughly  tamped  with 
tampers  of  such  form  and  material  as 
the  circumstances  require. 

The  steel  shall  be  accurately  placed  in 
the  forms  and  secured  against  disturb- 
ance  while  the  concrete  is  being  placed 
and  tamped,  and  every  precaution  shall 
be  taken  to  insure  that  the  steel  occupies 
exactly  the  position  in  the  finished  work 
as  shown  on  the  drawing. 

Before  the  placing  of  concrete  is  sus- 
pended the  joint  to  be  formed  shall  be  in 
such  place  and  shall  be  made  in  such 
manner  as  will  not  injure  the  strength  of 
the  completed  structure. 

Whenever  fresh  concrete  joins  con- 
crete that  has  set,  the  surface  of  the  oíd 


110  CONCRETE    1NSPECTI0N. 

concrete  shall  be  roughened,  cleaned  and 
thoroughly  slushed  with  a  grout  of  neat 
cement  and  water. 

No  work  shall  be  done  in  freezing 
weather,  except  when  the  influence  of 
frost  is  entirely  excluded. 

Until  sufficient  hardening  of  the  con- 
crete has  occurred,  the  structural  parts 
shall  be  protected  against  the  effects  of 
freezing,  as  well  as  against  vibrations  and 
loads. 

When  the  concrete  is  exposed  to  a  hot 
or  dry  atmosphere  special  precautions 
shall  be  taken  to  prevent  premature  dry- 
ing  by  keeping  it  moist  for  a  period  of  at 
least  twenty-four  hours  after  it  has  taken 
its  initial  set.  This  shall  be  done  by  a 
covering  of  wet  sand,  cinders,  burlap,  or 
by  continuous  sprinkling,  or  by  some 
other  me.thod  equally  effective  in  the 
opinión  of  the  Commissioner  of  Public 
Buildings. 

If  during  the  hardening  period  the 
temperature  is  continually  above  70°  F., 
the  side  forms  of  concrete  beams  and  the 
forms  of  floor  slabs  up  to  spans  of  eight 
feet  shall  not  be  removed  before  four 
days.  The  remaining  forms  and  sup- 
ports  not  before  ten  days  from  the  com- 
pletion  of  tamping. 

If  during  the  hardening  period  the 
temperature  falls  below  70°  F.,  the  side 
forms  of  concrete  beams  and  the  forms 
or    floor    slabs    up    to     spans    of  8  ft. 


SPECIFICATlONS.  111 

shall  not  be  removed  before  seven  days; 
the  remaining  forms  and  the  supports 
not  before  fourteen  days  from  the  com- 
pletion  of  the  tamping.  But  if  during 
the  hardening  period  the  temperature 
falls  below  35°  F.,  the  time  for  hardening 
shall  be  extended  by  the  time  during 
which  the  temperature  was  below  35°  F. 

Forms  of  concrete  shall  be  sufíiciently 
substantial  to  preserve  their  accurate 
shape  until  the  concrete  has  set,  and 
shall  be  sufíiciently  tight  so  as  not  to 
permit  any  part  of  the  concrete  to  leak 
out  through  cracks  or  holes. 

Before  placing  the  concrete,  the  inside 
of  the  forms  shall  be  thoroughly  cleaned 
of  all  dirt  and  rubbish,  the  forms  of  all 
beams,  girders  and  columns  being  con- 
structed  with  a  temporary  opening  in  the 
bottom  for  this  purpose. 

If  loading  tests  are  considered  neces- 
sary  by  the  Commissioner  of  Public 
Buildings,  they  shall  be  made  in  accord- 
ance  with  his  instructions,  but  the 
stresses  induced  in  all  parts  of  a  struc- 
tural  member  by  its  test  load  shall  be 
the  same  as  if  the  member  were  subject- 
ed  to  twice  the  dead  load  plus  twice  the 
assumed  load. 

All  tests  of  material  herein  required 
shall  be  made  by  testing  laboratories  of 
recognized  standing,  and  certified  copies 
of  such  test  reports  shall  be  filed  with 
the  Commissioner  of  Public  Buildings. 


112  CONCRETE    1NSPECTI0N. 

THE  NATIONAL  ASSOCIATION  OF 

CEMENT     USERS'     PROPOSED 

STANDARD  BUILDING  REG- 

ULATIONS  FOR  THE  USE 

OF  REINFORCED 

CONCRETE. 


I.     General. 

1.  The  term  "Reinforced  Concrete" 
shall  be  understood  to  mean  an  approved 
concrete  which  has  been  reinforced  by 
metal  in  some  form  so  as  to  develop  the 
compressive  strength  of  the  concrete. 

2.  Reinforced  concrete  may  be  used 
for  all  clases  of  buildings  if  the  design  is 
in  accordance  with  good  engineering 
practice  and  stresses  are  figured  as  indi- 
cated  in  these  regulations. 

3.  There  shall  be  no  limit  upon  the 
height  of  buildings  of  reinforced  con- 
crete except  as  limited  by  the  require- 
ments  in  these  regulations. 

4.  Before  permission  is  granted  by  the 
Building  Department  to  erect  any  rein- 
forced concrete  building,  complete  plans, 
accompanied  by  specifications,  signed  by 
the  engineer  and  architect,  must  be  filed 
with  the  Building  Department  and  re- 
main  on  file  for  public  inspection  until 
the  building  is  completed. 

5.  The  Building  Department  shall  have 
access  to  the  computations,  which  shall 
give  the  loads  assumed  separately,  such 


SPEC1FICAT10NS.  113 

as  dead  and  live  loads,  wind  and  impact, 
if  any,  and  the  resulting  stresses. 

6.  The  specifications  shall  state  the 
qualities  of  the  materials  to  be  used  for 
making  the  concrete,  and  the  propor- 
tions  in  which  they  are  to  be  mixed. 

7.  Upon  the  completion  of  the  building 
the  engineer  and  architect  shall  issue, 
under  the  approval  of  the  Building  De- 
partment, signed  certificates,  to  be  post- 
ed  on  each  floor  of  the  building,  stating 
the  safe  carrying  capacity  per  square 
foot. 

8.  There  shall  be  kept  an  exact  record 
of  the  progress  of  each  operation  where 
the  same  can  be  inspected  by  the  Build- 
ing Department.  These  records  shall  show 
the  date  of  placing  of  all  the  concrete 
and  date  of  removal  of  the  forms,  and 
must  be  turned  over  to  the  Building  De- 
partment when  the  building  is  com- 
pleted. 

9.  Reinforced  concrete  walls  may  be 
used  in  place  of  brick  or  stone  walls 
with  reduced  thickness.  Curtain  walls 
shall  not  be  less  than  4  ins.  thick. 

10.  Concrete  walls  must  be  reinforced 
in  both  directions.  The  máximum  spac- 
ing  of  reinforcing  bars  shall  be  18  in. 
centers,  reinforcement  in  eitheror  both 
faces  of  the  wall  being  considered.  Re- 
inforcement shall  be  not  less  than  one- 
fourth  of  1  per  cent. 

11.  Wherever   floor   constructions   are 


114  CONCRETE    INSPECTION. 

built  with  a  combination  of  tile  or  other 
fillers  between  joists,  the  following  rules 
regarding  the  dimensions  and  methods 
of  calculations  of  construction  shall  be 
observed: 

(a)  Ratio  of  mínimum  depth  to  clear 
span  of  joist  shall  not  be  greater  than 
one  to  eighteen. 

(b)  Wherever  a  portion  of  the  slab 
above  the  tile  joist  shall  be  considered  as 
acting  as  a  tee-beam  section,  the  slab 
portion  must  be  cast  monolithic  with  the 
joist  and  must  have  a  mínimum  thickness 
of  at  least  2  ins.  on  all  spans.  Otherwise 
all  regulations  applying  to  tee  beams 
shall  apply  to  tile  and  joist  construction. 

(c)  Where  the  joists  are  figured  as  rec- 
tangular beams,  in  accordance  with  the 
standard  regulations  for  this  type  of 
beams,  the  slab  shall  be  considered  as  in- 
dependent  of  the  structural  part  of  the 
building. 

(d)  Wherever  porous  tiles,  or  other 
materials  which  by  their  nature  will  ab- 
sorb  water  from  the  concrete,  are  used 
between  the  joists,  care  must  be  taken  to 
thoroughly  satúrate  the  tiles  or  other 
materials  with  water  immediately  before 
the  concrete  is  placed. 

(e)  Reinforcement  for  slabs  over  joist 
construction  below  30  in.  centers  need 
not  be  closer  than  24  ins.  in  each  direc- 
tion. 


SPECIFICA  TIONS.  1 1 5 

II.    Materials. 

12.  a.  Cement. — Only  Portland  cement 
shall  be  used  in  reinforced  concrete 
structures.  Portland  cement  shall  meet 
the  requirements  of  the  Standard  Specifi- 
cations  for  Cement  of  the  American  So- 
ciety  for  Testing  Materials.  (See  Stand- 
ard No.  1  of  the  National  Association  of 
Cement  Users.) 

13.  Tests  of  cement  used  in  building 
operations  shall  be  made  from  time  to 
time  under  the  supervisión  of  the  Build- 
ing Department  in  accordance  with  the 
preceding  specifications.  No  brand  of 
cement  which  has  not  met  these  require- 
ments shall  be  used. 

14.  b.  Aggregates. — Extreme  care  shall 
be  exercised  in  selecting  the  aggregate 
for  mortar  and  concrete,  and  careful 
tests  must  be  made,  where  any  doubt  ex- 
ists,  of  the  materials  for  the  purpose  of 
determining  their  qualities  and  the  grad- 
ing  necessary  to  secure  máximum  densi- 
ty  or  a  mínimum  percentage  of  voids. 

15.  Fine  aggregate  shall  consist  of 
sand,  crushed  stone  or  gravel  screenings, 
passing  when  dry  a  screen  having  one- 
quarter  inch  diameter  holes,  and  not 
more  than  6  per  cent  passing  a  sieve 
having  100  meshes  per  lineal  inch.  It 
shall  be  of  clean,  silicious  material  free 
from  vegetable  loam  or  other  deleterious 
matter. 


116  CONCRETE    INSPECTION. 

16.  Mortars  composed  of  one  part 
Portland  cement  and  three  parts  fine  ag- 
gregate  by  weight  when  made  into  bri- 
quets  should  show  a  tensile  strength  of 
at  least  70  per  cent  of  the  strength  of  1 :3 
mortar  of  the  same  consistency  made 
with  the  same  cement  and  standard  Ot- 
tawa  sand. 

17.  Coarse  aggregate  shall  consist  of 
inert  material,  such  as  crushed  stone  or 
gravel,  which  is  retained  on  a  screen 
having  one-quarter  inch  diameter  holes, 
the  particles  shall  be  clean,  hard,  durable 
and  free  from  all  deleterious  material. 
The  máximum  size  of  the  coarse  aggre- 
gate shall  be  such  that  it  will  not  sep- 
árate from  the  mortar  in  laying  and  will 
not  prevent  the  concrete  fully  surround- 
ing  the  reinforcement  or  filling  all  parts 
of  the  forms. 

18.  The  máximum  size  for  reinforced 
concrete  shall  be  such  that  all  the  aggre- 
gate shall  pass  a  one  and  one-quarter 
inch  diameter  ring. 

19.  Cinder  concrete  shall  not  be  used 
for  reinforced  concrete  structures;  it  may 
be  used  for  fire  proofing.  Where  cinders 
are  used  as  the  coarse  aggregate  they 
shall  be  composed  of  hard,  clean,  vitre- 
ous  clinker,  free  from  sulphides,  un- 
burned  coal  or  ashes. 

20.  c.  Reinforcement. — Médium  steel 
for    reinforcement   of   concrete   shall   be 


SPECIFICA  TIONS.  117 

made  from  billets  and  shall  conform  to 
the  requirements  of  the  specifications  for 
structural  steel  adopted  by  the  American 
Railway  Engineering  and  Maintenance 
of  Way  Association. 

21.  High  carbón  steel  shall  be  made 
entirely  from  new  billets,  having  (1)  a 
desired  ultímate  strength  of  88,000  lbs. 
per  sq.  in.  with  an  allowable  range  of 
8,000  lbs.  from  the  desired  ultímate 
strength,  (2)  an  elongation  in  per  cent  in 

1,200,000 

eight  (8)  inches  of and 

ultímate  strength 
(3)  capable  of  cold  bending  180  degrees 
around     four     diameters     without    frac- 
ture. 

22.  Where  wire  or  rods  up  to  one- 
quarter  inch  diameter  are  used  for  rein- 
forcement  of  slabs  or  for  the  prevention 
of  shrinkage  cracks,  either  material 
manufactured  from  the  Bessemer  billet 
(not  rerolled  rails)  or  drawn  from  basic 
open  hearth  steel  may  be  used. 

III.     Details  of  Construcción. 

23.  a.  Mixing. — General. — The  ingredi- 
ents  of  concrete  shall  be  thoroughly 
mixed  to  the  desired  consistency,  and  the 
mixing  shall  continué  until  the  cement  is 
uniformly  distributed  and  the  mass  is 
uniform  in  color  and  homogeneous. 

24.  Methods  of  measurement  of  the 
proportions    of    the    various    ingredients, 


118  CONCRETE    INSPECTION. 

including  the  water,  shall  be  nsed,  which 
will  secure  sepárate  uniform  measure- 
ments  at  all  times. 

25.  Machine  Mixing. — When  the  con- 
ditions  will  permit,  a  machine  mixer  of  a 
type  which  insures  the  proper  mixing  of 
the  materials  throughout  the  mass  shall 
be  used. 

26.  Hand  Mixing. — When  it  is  neces- 
sary  to  mix  by  hand,  the  mixing  shall  be 
on  a  water-tight  platform,  and  especial 
precautions  must  be  taken  to  turn  the 
materials  until  they  are  homogeneous  in 
appearance  and  color. 

27.  Consistency. — The  materials  must 
be  mixed  wet  enough  to  produce  a  con- 
crete of  such  a  consistency  as  will  flow 
into  the  forms  and  about  the  metal  rein- 
forcement,  and  which,  on  the  other  hand, 
can  be  conveyed  from  the  mixer  to  the 
forms  without  separation  of  the  coarse 
aggregate  from  the  mortar. 

28.  Retempering  mortar  or  concrete — 
i.  e.,  remixing  with  water  after  it  has 
partially  set — shall  not  be  permitted. 

29.  b.  Placing  of  Concrete. — General. — 
Concrete  shall  be  placed  in  the  work  im- 
mediately  after  mixing  and  deposited  and 
rammed  or  agitated  by  suitable  tools  in 
such  a  manner  as  to  produce  thoroughly 
compact  concrete  of  máximum  density. 
No  concrete  should  be  placed  until  the 
reinforcement  has  been    placed  and  firmly 


SPECíFICATIONS.  113 

secured   by   wiring  or   other  methods   to 
prevent  displacement. 

30.  The  faces  of  concrete  exposed  to 
premature  drying  shall  be  kept  damp  for 
a  period  of  at  least  seven  days. 

31.  Before  placing  the  concrete  care 
shall  be  taken  to  see  that  the  forms  are 
substantial  and  thoroughly  wetted  and 
the  space  to  be  occupied  by  the  concrete 
free  from  debris.  When  the  placing  of 
the  concrete  is  suspended,  all  necessary 
grooves  for  joining  future  work  shall  be 
made  before  the  concrete  has  liad  time 
to  set. 

32.  When  work  is  resumed,  concrete 
previously  placed  shall  be  roughened, 
thoroughly  cleansed  of  foreign  material 
and  laitance,  drenched  and  slushed  with 
a  mortar  consisting  of  one  part  Portland 
cement  and  not  more  than  two  parts  fine 
aggregate. 

33.  Placing  in  Water. — Concrete  should 
not  be  placed  in  water,  unless  unavoida- 
ble.  Where  concrete  must  be  placed  un- 
der  water,  unusual  care  must  be  taken  to 
prevent  the  cement  from  being  floated 
away. 

34.  Freezing  Weather.— Concrete  shall 
not  be  mixed  or  deposited  at  a  freezing 
temperature  unless  special  precautions 
are  taken  to  avoid  the  use  of  materials 
containing  frost  or  covered  with  ice 
crystals,   and   to   provide   means   to  pre- 


120  CONCRETE    1NSPECTION. 

vent  the  concrete  from  freezing  after  be- 
ing  placed  in  position  and  until  it  has 
thoroughly  hardened. 

35.  c.  Placing  of  Reinforcement. — The 
reinforcement  shall  be  accurately  located 
in  the  forms  and  secured  against  dis- 
placement. 

36.  d.  Joints. — Reinforcement. — Wher- 
ever  it  is  necessary  to  splice  reinforce- 
ment by  means  of  lapping,  the  length  of 
the  lap  shall  be  determined  upon  the  ba- 
sis  of  the  safe  bond  stress  and  the  stress 
in  the  bar  at  the  point  of  splice,  or  a 
connection  shall  be  made  between  the 
bars  of  sufficient  strength  to  carry  the 
ctress.  Splices  at  the  point  of  máximum 
stress  must  be  avoided. 

37.  In  columns  large  bars  shall  be 
properly  butted  and  spliced.  Small  bars 
may  be  treated  as  indicated  in  paragraph 
36. 

38.  Concrete. — Reinforced  concrete 
work  shall  be  stopped  at  such  points  that 
the  joints  will  have  the  least  possible  ef- 
fect  on  the  strength  of  the  structure. 
Footings  shall  be  cast  to  their  full  depth 
at  one  operation. 

(a)  Columns. — Work  in  columns  shall 
be  stopped  at  the  under  side  of  the  low- 
est  beam  or  girder  bearing  on  the  col- 
umn. 

(b)  Beams  and  Girders. — Construction 
joints  in  beams  and  girders  shall  be  ver- 


SPEC1FICATI0NS.  121 

tical  and  within  the  middle  third  of  the 
span.  Any  concrete  which  may  run  past 
the  bulkheads  must  be  cleaned  up  before 
the  concreting  of  the  next  section  is 
started.  Where  brackets  are  used,  the 
bracket  shall  be  considered  as  a  part  of 
the  beam  or  girder. 

(c)  Slabs. — Construction  joints  in  slabs 
shall  be  near  the  center  of  the  span.  No 
joint  will  be  allowed  between  slab  and 
beam  or  girder. 

39.  e.  Removal  of  Forms. — Under  no 
consideration  shall  forms  be  removed 
until  the  concrete  has  hardened  suffi- 
ciently  to  permit  their  removal  with 
safety. 

40.  Floor  Slabs  and  Beams. — Forms 
shall  not  be  removed  from  floor  slabs  in 
less  than  seven  days.  Sides  of  beams 
may  be  removed  at  the  same  time  as  the 
floor  slabs  provided  original  supports 
under  beams  and  girders  are  left  in 
place. 

41.  Columns. — Where  original  supports 
remain  under-  beams  and  girders  coming 
to  the  columns,  the  forms  shall  not  be 
removed  from  the  columns  in  less  than 
four  days. 

42.  Beam  and  Girder  Supports. — The 
original  supports  for  all  beams  and  gir- 
ders must  remain  in  place  at  least  ten 
days,  but  all  beams  and  girders  having 
more     than     30     ft.     span     from     center 


122  CONCRETE    INSPBCT10N. 

to  center  of  support  shall  be  considered 
as  special  cases  and  shall  be  subject  to 
inspection  of  the  Building  Department 
before  removal  of  supports. 
IV.  Design. 
43.  a.  General  Assumptions. — Internal 
Stresses. — As  a  basis  for  calculations  for 
the  strength  of  reinforced  concrete  con- 
struction,  the  following  assumptions 
shall  be  made: 

(a)  A  plañe  section  before  bending  re- 
mains  plañe  after  bending. 

(b)  The  modulus  of  elasticity  of  con- 
crete in  compression  within  the  usual 
limits  of  working  stresses  is  constant. 

(c)  In  calculating  the  moment  of  re- 
sistance  of  beams  the  tensile  stresses  in 
the  concrete  shall  be  neglected. 

(d)  Perfect  adhesión  is  assumed  be- 
tween  concrete  and  reinforcement.  Un- 
der  compressive  stresses  the  two  mate- 
rials  are  therefore  stressed  in  proportion 
to  their  moduli  of  elasticity  and  their 
distance  from  the  neutral  axis. 

(e)  The  ratio  of  the  modulus  of  elas- 
ticity of  steel  to  the  modulus  of  elasticity 
of  concrete  shall  be  assumed  to  be  15. 

(f)  No  allowance  shall  be  made  for 
tensión  in  concrete. 

(g)  Initial  stress  ín  the  reinforcement 
due  to  contraction  or  expansión  in  the 
concrete  may  be  neglected. 

(h)   In  columns  the  ratio  of  least  di- 


SPECIFICA  TIONS.  123 

ameter  to  height  shall  be  taken  as  one- 
fifteenth.  Greater  ratios  shall  be  de- 
duced  by   satisfactory   column   formulas. 

44.  Length  of  Beams  and  Slabs. — The 
span  length  for  beams  and  slabs  shall  be 
taken  as  the  distance  from  center  to  cen- 
ter  of  supports,  but  shall  not  be  taken  to 
exceed  the  clear  span  plus  the  depth  of 
beam  or  slab.  Brackets  shall  not  be  eon- 
sidered  as  reducing  the  clear  span. 

45.  Length  of  columns  shall  be  taken 
as  the  máximum  unsupported  length. 

46.  Where  slabs  and  beams  are  figured 
as  simple  beams  the  length  shall  be  con- 
sidered  as  the  clear  distance  betwcen 
supports  excluding  brackets. 

47.  b.  Loads. — The  dead  load  shall  in- 
clude  the  weight  of  the  strcture  and  all 
fixed  loads  and  forces. 

48.  The  weight  of  the  reinforced  con- 
crete shall  be  taken  as  150  pounds  per 
cubic  foot. 

49.  The  live  load  shall  include  all  loads 
and  forces  which  are  variable. 

The  mínimum  live  load  for  floors  and 
roofs  shall  be  as  generally  provided  by 
building  codes. 

50.  Roof  and  Floor  Loads. — The  roof 
shall  be  figured  to  carry  30  pounds  live 
load  per  square  foot  unless  otherwise 
noted. 

51.  A  reduction  of  live  load  coming  to 
the   column   supporting   the   floor   below 


124  CONCRETE    1NSPECTI0K. 

the  roof  of  5  per  cent  to  be  allowed  and 
a  further  reduction  of  5  per  cent  of  the 
live  load  of  each  story  below  until  the 
total  reduction  shall  amount  to  50  per 
cent  of  the  live  load  of  any  floor,  after 
which  all  loads  shall  be  figured  net  to 
the  foundations.  These  reductions  shall 
not  apply  to  storage  warehouses. 

52.  Reduction  of  Loads. — No  reduction 
of  loads  shall  be  allowed  for  figuring 
floor  slabs. 

53.  No  reduction  of  loads  shall  be  al- 
lowed for  figuring  beams. 

54.  A  reduction  of  15  per  cent  live 
load  may  be  allowed  in  figuring  the  gir- 
ders,  except  in  buildings  used  for  stor- 
age purposes. 

55.  In  assuming  the  load  coming  to 
the  columns  all  beams  and  girders 
shall  be  considered  as  carrying  a 
net  load  consisting  of  100  per  cent  each 
of  live  and  dead  load,  subject  to  the 
above  reductions. 

56.  c.  Bending  Moments. — Slabs. — The 
bending  moment  of  slabs  uniformly  load- 
ed  and  supported  at  two  sides  only  shall 
be  taken  as  Vs  wl2  where  w  —  unit  load 
and  l  =  span. 

57.  Continuous  Slabs. — For  interior 
slabs  overhanging  two  or  more  supports 
the  bending  moment  shall  be  taken  as 
1/12  wl2.  The  reinforcement  at  the  top 
of   the    slab   over    supports   must    equal 


SPEC1FICA  TIONS.  125 

that  used  at  the  center.  The  reinforce- 
ment  in  the  bottom  of  the  slab  must 
equal  at  least  %  of  that  used  at  center. 

58.  Slabs  Reinforced  in  Both  Direc- 
tions.— Slabs  that  are  reinforced  in  both 
directions  and  supported  on  four  sides 
and  fully  reinforced  over  the  supports 
(the  reinforcement  passing  into  the  ad- 
joining  slabs)  may  be  figured  on  the  ba- 

wl2 
sis  of  bending  moments  equivalent  to  — 

F 
for  load  in  each  direction.  When  span 
under  consideration  is  not  continuous,  F 
=  8;  when  continuous  over  one  support, 
F  =  10;  when  continuous  over  both  sup- 
ports, F  =  12.  The  distribution  of  the 
loads  to  be  determined  by  the  formula: 
V 

~  V  +  b* 
in  which  r  equals  proportion  of  load  car- 
ried    by    the    transverse    reinforcement,    L 
equals     length     of     span     and     b     equals 
breadth  of  slab. 

59.  The  slab  área  may  be  reduced  by 
one-half,  as  above  figured,  when  the  re- 
inforcement is  parallel  to  and  not  farther 
from  the  supports  than  one-quarter  of 
the  shortest  side. 

The  reinforcement  spanning  the  short- 
est direction  shall  be  below  the  rein- 
forcement spanning  the  longer  direction, 
and  shall  not  be  further  apart  than  2y2 


126  CONCRETE    INSPECTION. 

times  the  thickness  of  the  floor  including 
the  finish. 

60.  Simple  Beams. — The  bending  mo- 
ment  of  beams  supported  at  the  ends 
only  shall  be  figured  as  of  simple  beams. 

61.  Partially  Restrained  Beams. — 
Beams  supported  at  one  end  and  con- 
tinuous  at  the  other  to  be  figured  par- 
tially restrained  with  a  bending  moment 
of  eight-tenths  (0.8)  that  of  a  simple 
beam. 

When  the  overall  vertical  distance  of 
the  tensión  members  is  greater  than  one- 
sixth  of  the  total  depth  of  the  beam  the 
stresses  in  each  member  shall  be  com- 
puted  in  proportion  to  the  distance  from 
the  neutral  axis. 

62.  Beams  supporting  rectangular  slabs 
reinforced  in  both  directions  shall  be  as- 
sumed  to  take  the  following  load:  The 
beams  on  which  the  shortest  sides  of  the 
slab  rest  shall  take  the  load  of  that  por- 
tion  of  the  slab  formed  by  the  isósceles 
triangle  having  this  side  as  its  base  and 
half  this  side  as  its  height.  The  load 
from  the  remaining  portion  of  the  slab 
shall  go  to  the  beams  on  which  the  long 
side  of  the  slab  rests. 

63.  Continuous  Beams. — When  beams 
or  girders  are  continuous  over  two  or 
more  supports,  the  interior  beams  may 
be  considered  as  partially  restrained,  and 
the  bending  moments  at  the  center  and 


SPECIFICA  T10NS.  127 

support  figured  as  two-thirds  (2/3)  that 
of  a  simple  beam,  unless  the  concrete  at 
the  bottom  of  the  beam  at  the  support 
shall  by  this  consideration  receive  excess 
compression. 

64.  Tee  Beams. — In  beam  and  slab  con- 
struction,  an  effective  metallic  bond 
should  be  provided  at  the  junction  of  the 
beam  and  slab.  When  the  principal  slab 
reinforcement  is  parallel  to  the  girder, 
transverse  reinforcement  shall  be  nsed 
extending  over  the  girder  and  well  into 
the  slab. 

65.  Where  adequate  bond  between  slab 
and  web  of  beam  is  provided,  the  slab 
may  be  considered  as  an  integral  part  of 
the  beam,  but  its  effective  width  shall 
not  exceed  one-eighth  (%)  of  the  span 
length  of  the  beam  on  either  side  of  the 
beam. 

66.  In  the  design  of  tee  beams  acting 
as   continuous   beams,   due   consideration     * 
should     be     given    to    the    compressive 
stresses  at  the  support  at  the  bottom  of 
the  beam. 

67.  d.  Working  Stresses. — Concrete 
composed  of  materials  meeting  the  re- 
quirements  of  these  regulations,  mixed  in 
proportion  of  one  part  of  cement  and 
six  parts  of  aggregate  (fine  and  coarse), 
shall  develop  a  compressive  strength  of 
2,000  Ibs.  per  sq.  in.  in  28  days  when 
tested  as  8  in.  diameter  cylinders  16  ins. 


128  CONCRETE    INSPECTION. 

long  under  laboratory  conditions  of 
manufacture  and  storage,  using  the  same 
consistency  as  is  used  in  the  field.  When 
the  proportion  of  cement  is  increased, 
using  the  best  quality  of  aggregates,  an 
increase  may  be  made  in  all  w  rking 
stresses  proportional  to  the  increase  in 
compressive  strength  at  28  days,  as  de- 
termined  by  actual  tests.  On  this  basis 
the  following  working  stresses  shall  be 
allowed  in  construction: 

68.  Bearing  compression,  650  lbs.  per 
sq.  in. 

69.  Compression  in  extreme  fiber,  650 
lbs.  per  sq.  in.  With  increase  of  15  per 
cent  near  supports  in  continuous  beams. 

70.  Axial  compression  in  columns 
without  hoops,  450  lbs.  per  sq.  in.  and 
6,750  lbs.  per  sq.  in.  on  vertical  rein- 
forcement. 

71.  Axial  compression  in  columns  with 
1  per  cent  of  hooping,  540  lbs.  per  sq.  in., 
and  6,750  lbs.  per  sq.  in.  of  vertical  rein- 
forcement. 

72.  Axial  compression  in  columns  with 
1  per  cent  hooping  and  1  to  4  per  cent 
of  vertical  reinforcement,  650  lbs.  per  sq. 
in.  on  the  concrete  and  9,750  on  the  ver- 
tical reinforcement. 

Bars  composing  longitudinal  reinforce- 
ment shall  be  straight  and  shall  have 
sumcient  lateral  support  to  be  securely 
held  in  place  until  the  concrete  is  set. 


SPEC1FICAT10NS.  129 

The  clear  spacing  of  bands  or  hoops 
shall  be  not  greater  than  one-fourth  the 
diameter  of  the  inclosed  column.  Ade- 
quate  means  must  be  provided  to  hold 
bands  or  hoops  in  place  so  as  to  form  a 
colum  f  the  core  of  which  shall  be 
straight  and  well  centered. 

Bending  stresses  due  to  eccentric 
loads  must  be  provided  for  by  increasing 
the  section  until  the  máximum  stress 
does  not  exceed  the  valúes  above  speci- 
fied. 

73.  Compression  on  columns  rein- 
forced  with  structural  steel  units  which 
thoroughly  encase  the  concrete  core,  540 
lbs.  per  sq.  in.  on  the  concrete  and  8,100 
lbs.  per  sq.  in.  on  the  structural  steel. 

74.  Web  Stresses. — In  calculating  web 
reinforcement  the  concrete  shall  be  -con- 
sidered  to  carry  40  lbs.  per  sq.  in.,  the 
remainder  to  be  provided  for  by  means 
of  reinforcement  in  tensión. 

Members  of  web  reinforcement  shall 
be  embedded  in  the  compression  portion 
of  the  beam  so  that  adequate  bond 
strength  is  provided  to  fully  develop  the 
assumed  strength  of  all  shear  reinforce- 
ment. They  shall  not  be  spaced  to  ex- 
ceed three-fourths  of  the  depth  of  the 
beam  in  that  portion  where  the  shearing 
stresses  exceed  the  allowable  shearing 
valué  of  the  concrete.  Web  reinforce- 
ment,   unless    rigidly   attached,    shall    be 


130  CONCRETE    1NSPECTION. 

placed  at  right  angles  to  the  axis  of  the 
beam  and  looped  around  the  extreme 
tensión  member. 

75.  Bond  between  plain  bars  and  con- 
crete, 80  lbs.  per  sq.  in.  of  surface  of 
bar;  where  adequate  mechanical  bond  is 
provided  the  stress  shall  not  exceed  150 
lbs.  per  sq.  in.  of  surface  of  bar. 

76.  The  ratio  of  modulus  of  elasticity 
cf  concrete  to  steel  shall  be  considered 
as  one  to  fifteen. 

77.  The  allowable  tensile  stress  in  re- 
inforcement  to  be  16,000  pounds  per 
square  inch  for  médium  steel  and  20,000 
pounds  per  square  inch  for  high  carbón 
steel  with  adequate  mechanical  bond. 

78.  The  compressive  stress  in  the  steel 
remforcement  to  be  fifteen  times  the 
allowed  comprensión  in  concrete  in 
which  the  steel  is  embedded. 

79.  e.  Fireproofing. — The  main  rem- 
forcement in  columns  shall  be  protected 
by  a  mínimum  of  two  inches  of  concrete, 
reinforcement  in  girders  and  beams  by 
ll/>  ins.  and  floor  slabs  by  1  in. 

SPECIFICATIONS  FOR  MATERIALS 

AND   WORKMANSHIP    FOR 

ARCH  BRIDGE  CON- 

STRUCTION.* 

Cement. — No   cement  will  be  allowed 

to  be  used  except  established  brands  of 


*Extracts    from    the    Specifications    of    the 
Concrete  Steel  Engineering  Co.,  New  York. 


SPECIFICAT10NS.  131 

high  grade  Portland  cement  which  has 
been  in  successful  use  under  similar  con- 
ditions  to  the  work  proposed  for  at  least 
3  years,  and  has  been  seasoned  or  sub- 
jected  to  aeration  for  at  least  30  days 
before  leaving  the  factory.  All  cement 
shall  be  dry  and  free  from  lumps,  and 
immediately  upon  receipt  shall  be  stored 
in  a  dry,  well  covered  and  ventilated 
place,  thoroughly  protected  from  the 
weather.  If  required  the  contractor 
shall  furnish  a  certified  statement  of  the 
chemical  composition  of  the  cement  and 
of  the  raw  material  from  which  it  is 
manufactured. 

The  fineness  of  the  cement  shall  be 
such  that  at  least  90  per  cent  will  pass 
through  a  sieve  of  No.  40  wire,  Stubbs 
gage,  having  10,000  openings  per  square 
inch,  and  at  least  75  per  cent  will  pass 
through  a  sieve  of  No.  45  wire,  Stubbs 
gage,  having  40,000  openings  per  square 
inch. 

Samples  for  testing  may  be  taken  from 
every  bag  or  barrel,  but  usually  for  tests 
*  of  100  barréis  a  sample  will  be  taken 
from  every  tenth  barrel.  The  samples 
will  be  mixed  thoroughly  together  while 
dry  and  the  mixture  be  taken  as  the 
sample  for  test. 

Tensile  tests  will  be  made  on  speci- 
mens  prepared  and  maintained  until 
tested  at  a  temperature  not  less  than  60° 


132  CONCRETE    INSPECTION. 

F.  Each  specimen  will  have  an  área  of 
1  sq.  in.  at  the  breaking  section,  and 
after  being  allowed  to  harden  in  moist 
air  for  24  hours  will  be  immersed  and 
maintained  under  water  until  tested. 

The  sand  used  in  preparing  test  speci- 
mens  shall  be  clean,  sharp,  crushed 
quartz  retained  on  a  sieve  of  30  meshes 
per  lineal  inch,  and  passing  through  a 
sieve  of  20  meshes  per  lineal  inch.  In 
test  specimens  of  1  cement  and  3  sand, 
no  more  than  12  per  cent  of  water  by 
weight  shall  be  used.  Specimens  pre- 
pared  from  a  mixture  of  1  part  cement 
and  3  parts  sand,  parts  by  weight,  shall 
after  7  days  develop  a  tensile  strength  of 
not  less  than  170  lbs.  per  sq.  in.  and  not 
less  than  240  lbs.  per  sq.  in.  after  28 
days.  Cement  mixed  neat  with  from  20 
per  cent  to  25  per  cent  of  water  to  form 
a  stiff  paste  shall  after  30  minutes  be 
appreciably  indented  by  the  end  of  a 
wire  1/12  in.  in  diameter  loaded  to  weigh 
%  Ib.  Cement  made  into  thin  pats  on 
glass  plates  shall  not  crack,  scale  ñor 
warp  under  the  following  treatment: 
Three  pats  will  be  made  and  allowed  to 
harden  in  moist  air  at  from  60°  to  70° 
R;  one  of  these  will  be  placed  in  fresh 
water  for  28  days,  another  will  be  placed 
in  water  which  will  be  raised  to  the  boil- 
irtg  point  for  6  hours  and  then  allowed 
to  cool,  and  the  third  is  to  be  kept  in  air 
of  the  prevailing  outdoor  temperature. 


SPEC1FICAT10NS.  133 

Portland  Cement  Concrete. — The  con- 
crete shall  be  composed  of  cement,  sand 
and  broken  stone  or  gravel  mixed  with 
clean  water  in  the  proportions  hereafter 
mentioned. 

The  sand  shall  be  clean,  sharp  and 
coarse,  or  coarse  and  fine  mixed,  free 
from  sewage,  mud,  clay  and  all  foreign 
matter. 

The  broken  stone  shall  be  clean  and 
hard,  broken  into  approximately  cubical 
pieces,  and  free  from  long,  thin  scales. 

The  gravel  shall  be  of  assorted  sizes 
screened  or  washed  entirely  free  from 
clay,  loam  or  foreign  matter,  and  be  free 
from  scale,  slime  or  humus. 

Whenever  the  amount  of  work  to  be 
done  is  sufíicient  to  justify  it,  and  for  all 
work  exceeding  1,000  cu.  yds.,  approved 
mixing  machines  shall  be  used.  The  in- 
gredients  shall  be  placed  in  the  machine 
in  a  dry  state  and  in  the  volumes  speci- 
fied,  and  be  thoroughly  mixed,  after 
which  clean  water  shall  be  added  and 
the  mixing  continued  until  the  wet  mix- 
ture is  thorough  and  the  mass  uniform. 
The  mixture  shall  be  sufiíciently  wet  for 
the  water  to  come  to  the  surface  with 
modérate  ramming.  As  soon  as  the  batch 
is  mixed  it  must  be  deposited  in  the 
work  without  delay.  For  small  bridges, 
if  the  mixing  is  done  by  hand,  the  cem- 
ent and  sand  shall  first  be  thoroughly 
mixed  dry,  in  the  proportions  specified. 


134  CONCREÍ E    INSPECTION. 

The  stone,  previously  drenched  with  wa- 
ter, shall  then  be  deposited  in  this  mix- 
ture. Clean  water  shall  be  added  and 
the  mass  be  thoroughly  mixed  and 
turned  over  until  each  stone  is  covered 
with  mortar,  and  the  batch  be  deposited 
without  delay. 

The  concrete  shall  be  deposited  in  lay- 
ers  of  6  or  8  ins.  and  be  thoroughly 
rammed  until  all  voids  are  filled  and  the 
water  flushes  to  the  surface. 

The  grades  of  concrete  to  be  used  are 
as  follows: 

(a)  For  the  arches,  slabs,  girders, 
beams,  floors,  walls  subject  to  trans- 
verse  stress,  posts  and  tanks,  1  part 
Portland  cement,  2  parts  sand  and  4 
parts  broken  stone  that  will  pass  in  any 
direction  through  a  |.Já  in.  ring,  if  not 
otherwise  marked  on  plans. 

(b)  For  spandrel  walls,  1  part  Port- 
land cement,  3  parts  sand  and  6  parts 
broken  stone  or  gravel  that  will  pass 
through  a  2-in.  ring. 

(c)  For  the  piers,  abutments,  founda- 
tions  and  retaining  walls,  1  part  Port- 
land cement,  2>y2  parts  sand  and  7  parts 
broken  stone  or  gravel  that  will  pass 
through  a  3-in.  ring. 

Artificial  Stone. — (a)  All  keystones, 
brackets,  consoles,  dentiles,  pedestals, 
parapets,  hand  railings,  posts  and  panels 
and  other  ornamental  work  when  used, 
also  curbs  and  gutters,  shall  be  of  the 


SPEC1F1CA  T10NS.  135 

design  shown  on  plans  and  be  molded  in 
smooth  and  suitable  molds.  For  mold- 
ings  containing  curved  surfaces,  sharp 
curves,  carvings  or  other  delicate  work, 
the  molds  shall  be  plastered  with  a  semi- 
liquid  mortar  composed  of  1  part  cem- 
ent  and  2  parts  of  fine  sharp  sand.  The 
mortar  coating  must  be  followed  up 
with  a  backing  of  only  earth  damp  con- 
crete composed  of  1  part  cement,  2  parts 
sand  and  4  parts  of  fine  broken  stone,  or 
1  part  cement  and  6  parts  of  gravel  that 
will  pass  through  a  ¿4~in.  ring.  The 
concrete  backing  must  be  rammed  thor- 
oughly  in  thin  layers. 

(b)  For  plain  fíat  surfaces  the  concrete 
may  be  rammed  directly  against  the 
molds,  and  after  the  molds  have  been  re- 
moved all  exposed  surfaces  shall  be 
floated  to  a  smooth  finish  with  a  mortar 
the  same  as  specified  for  artificial  stone, 
care  being  taken  that  no  body  of  mortar 
is  left  on  the  face,  sufiicient  only  being 
used  to  fill  the  pores  and  give  a  smooth 
finish. 

When  pedestal  posts  carry  lamp  posts 
a  4-in.  wrought  iron  pipe  shall  be  built 
into  the  concrete  from  top  to  bottom, 
and  at  bottom  it  shall  be  connected  with 
a  3-in.  pipe  extending  under  the  side- 
walk  and  connected  with  gas  pipe  or 
electric  wire  conduit.  The  pipes  shall 
have  no  sharp  bends,  all  changes  in  di- 
rection  being  made  by  gentle  curves. 


136  CONCRETE    1NSPECT10N. 

Plastering. — No  plastering  will  be  al- 
lowed  on  the  exposed  faces  of  the  work, 
but  the  inside  faces  of  the  spandrel  walls 
covered  by  the  fill  shall  be  plastered 
with  mortar  composed  of  one  part  cem- 
ent  and  two  and  one-half  parts  sand,  the 
surface  being  well  dampened  before 
plastering. 

Mixtures.  —  The  volumes  of  cement, 
sand,  broken  stone,  or  gravel  in  all  mix- 
tures of  mortar  or  concrete  shall  be 
measured  loóse. 

Connections. — In  connecting  concrete 
already  set  with  new  concrete,  the  sur- 
face  shall  be  cleaned  and  roughened,  and 
mopped  with  a  mortar  composed  of  1 
part  cement  and  1  part  sand  to  cement 
the  parts  together. 

Expansión  Joints. — Expansión  joints 
shall  be  made  in  the  spandrel  walls,  cor- 
nices  and  parapets  of  each  arch  above 
the  springing  lines,  at  points  one-sixth 
span  from  the  springing  lines  and  at 
such  points,  if  any,  as  are  shown  on 
plan. 

Spandrels. — The  spandrel  walls  shall 
have  a  thickness  of  not  less  than  18  ins. 
at  any  point  and  a  thickness  at  bottom 
of  not  less  than  four-tenths  of  the  height 
of  the  wall  measured  from  the  top  of 
cornice. 

Arches.— For  square  arches  the  con- 
crete shall  be  laid  in  transverse  sections 


SPECIFICA  TIONS.  137 

of  the  full  width  of  the  arch,  between 
timber  forms  normal  to  the  center  line 
of  the  arch,  the  length  of  sections  being 
such  that  the  center  section,  or  a  pair  of 
intermedíate  or  end  sections,  shall  consti- 
tute  a  day's  work.  Work  shall  be  start- 
ed  at  the  center  section  and  carried  to- 
wards  the  ends,  the  end  sections  being 
laid  last. 

For  skew  arches  the  concrete  shall  be 
síarted  simultaneously  from  both  ends 
of  the  arch  and  be  built  in  longitudinal 
sections  at  least  5l/2  ft.  in  width,  and 
wide  enough  to  constitute  a  day's  work. 
The  concrete  shall  be  deposited  in  lay- 
crs,  each  layer  being  well  rammed  in 
place  before  the  previously  deposited 
layer  has  had  time  to  partially  set.  The 
work  shall  proceed  continuously  day  and 
night  if  necessary  to  complete  each 
longitudinal  section.  These  sections  while 
being  built  shall  be  held  in  place  by  sub- 
stantial  vertical  timber  forms,  parallel  to 
the  face  of  the  arch  and  to  each  other, 
and  these  forms  shall  be  removed  when 
the  section  has  set  sufficiently  to  admit 
of  it.  The  sections  shall  be  connected  as 
specified  under  "Connections,"  and  also 
by  steel  clamps  spaced  about  5  ft.  apart, 
connecting  the  adjacent  steel  ribs. 

Drainage.  —  Provisión  for  drainage 
shall  be  made  at  each  pier  as  follows:  A 
wrought  iron  pipe  of  sufficient  diameter 
shall  be  built  into  the  concrete,  extend- 


138  CONCRETE    INSPECTION. 

ing  from  the  center  of  each  space  over 
piers  to  the  soffit  of  the  arch  near  the 
springing  line,  and  project  1  in.  below 
the  soffit.  The  surface  of  the  concrete 
over  piers  shall  be  so  formed  that  any 
water  that  may  seep  through  the  fill 
above  will  be  drained  to  the  pipes.  The 
line  of  drainage  will  be  covered  with  a 
layer  of  broken  stone,  and  the  top  of 
pipes  will  be  provided  with  screens  to 
prevent  clogging. 

Steel. — Steel  ribs  shall  be  imbedded  in 
the  concrete  of  the  arches.  They  shall 
be  spaced  at  equal  distances  apart.  The 
design,  location,  dimensions,  and  con- 
nections  of  the  ribs,  also  the  sections  of 
steel  of  which  they  are  composed,  shall 
be  as  shown  on  the  plans. 

Steel  rods  shall  be  imbedded  near  the 
tensión  side  of  all  members  subjected  to 
transverse  stress.  No  reliance  will  be 
placed  on  the  adhesión  between  the  steel 
and  the  concrete,  but  our  patented  rods, 
specially  designed  for  this  purpose,  shall 
be  used  in  all  cases.  The  distance  of 
the  center  of  the  rods  from  the  outside 
of  the  concrete  shall  not  be  less  than  the 
diameter  of  the  rods.  All  steel  must  be 
free  from  paint  and  oil,  and  all  scale  and 
rust  must  be  removed  before  imbedding 
in  the  concrete. 

The  tensile  strength,  limit  of  elasticity 
and  ductility  shall  be  determined  from  a 


SPECIFICA  TIONS.  139 

test  piece  cut  from  the  finished  material 
and  turned  and  planed  parallel.  The 
área  of  cross  section  shall  not  be  less 
than  y2  sq.  in.;  the  elongation  shall  be 
measured  after  breaking  on  an  original 
length  of  8  ins.  Each  melt  shall  be 
tested  for  tensión  and  bending. 

Either  soft  or  médium  steel  may  be 
used  in  all  concrete  steel  structures.  If 
soft  steel  is  used  it  shall  have  an  ultí- 
mate strength  of  from  54,000  to  62,000 
lbs.  per  sq.  in.,  an  elastic  limit  of  not  less 
than  one-half  the  ultímate  strength,  shall 
elongate  not  less  than  25  per  cent  in  8 
ins.  and  bend  cold  180°  fíat  on  itself 
without  fracture  on  outside  of  bend.  If 
médium  steel  is  used  it  shall  have  an  ultí- 
mate strength  of  from  60,000  to  68,000 
lbs.  per  sq.  in.,  an  elastic  limit  of  not  less 
than  one-half  the  ultímate  strength,  shall 
elongate  not  less  than  22  per  cent  in  8 
ins.  and  bend  cold  180°  to  a  diameter 
equal  to  the  thickness  of  the  piece  tested 
without  fracture  on  outside  of  bend.  In 
tensión  tests  the  fracture  must  be  en- 
tirely  silky.  The  workmanship  must  be 
first  class. 

Casing. — When  concrete  facing  is  used 
all  piers,  abutments  and  spandrel  walls 
shall  be  built  in  timber  forms.  These 
forms  shall  be  substantial  and  unyield- 
ing,  of  the  proper  dimensions  for  the 
work  intended,  and  all  parts  in  contact 
with  exposed  faces  of  concrete  shall  be 


140  CONCRETE    INSPECTION. 

finished  to  a  perfectly  smooth  surface  by 
plastering  or  other  means,  so  that  no 
mark  or  imperfection  shall  be  left  on  the 
work. 

Concrete  Facing. — If  concrete  facing 
is  used  the  concrete  shall  be  deposited  in 
smooth  molds,  and  after  the  molds  have 
been  removed  the  exposed  flat  surfaces 
shall  be  finished  in  the  same  manner  as 
specified. 

If  the  arch  faces,  quoins  or  other  ex- 
posed surfaces  are  marked  to  represent 
masonry  or  other  división  lines,  either 
straight  or  curved,  are  shown  in  the 
faces  of  the  arch  or  spandrels,  such  divi- 
sión lines  shall  be  made  by  triangular 
moldings  of  wood  2  ins.  wide  and  1  in. 
deep,  fastened  to  the  casing  in  true  lines 
as  shown  on  plans.  The  face  of  the  arch 
at  intradós  shall  be  beveled  to  corre- 
spond,  and  all  angles  or  intersections  of 
the  moldings  shall  be  neatly  beveled  and 
fitted  in  a  workmanlike  manner  to  give  a 
smooth  finish.  Before  depositing  the 
concrete  the  moldings  shall  be  coated  in 
the  same  manner  as  specified  for  artificial 
stone. 

The  sofiits  of  the  arches  shall  be  float- 
ed  and  finished  in  the  same  manner  as 
specified  for  artificial  stone  (b). 

Other  Facing. — Tf  ashlar  masonry, 
boulder,  brick,  térra  cotta,  or  other  fac- 
ing is  used  on  the  work,  it  will  be  shown 


SPECIFICATIONS.  141 

or  noted  on  the  drawings,  and  a  specifi- 
cation  therefor  will  be  attached. 

Centering. — The  contractor  shall  build 
an  unyielding  fals.ework  or  centering. 
The  lagging  shall  be  dressed  to  a  uni- 
form  thickness  so  that  when  laid  it  shall 
present  a  smooth  surface,  or  it  shall  be 
made  smooth  by  plastering  or  other  effi- 
cient  means. 

In  framing  the  centers  allowance  shall 
be  made  for  settlement  of  centerings, 
deflection  of  arch  after  the  removal  of 
centerings  and  for  permanent  cambre. 
The  centers  shall  be  framed  for  a  rise  of 
arch  greater  than  the  rise  marked  on 
drawings  by  an  amount  equal  to  one- 
eight  hundredth  part  of  the  span,  and 
shall  not  be  struck  until  at  least  28  days 
after  the  completion  of  the  arch,  and  not 
until  the  fill  has  been  put  on.  Great  care 
shall  be  used  in  lowering  the  centers 
evenly  and  uniformly,  preferably  by 
means  of  sand  boxes,  so  as  not  to  throw 
undue  strains  upon  the  arches.  The 
tendency  of  the  centers  to  rise  at  the 
crown  as  they  are  loaded  at  the  haunches 
must  be  provided  for  in  the  design,  or,  if 
not,  the  centers  must  be  temporarily 
loaded  at  the  crown  and  the  load  so  reg- 
ulated  as  to  prevent  distortion  of  the 
arch  as  the  work  progresses. 

Water  Proofing. — After  the  completion 
of  the  arches  and  spandrels,  and  before 


142  CONCRETE    INSPECTION. 

any  fill  is  put  in,  the  top  surface  of  the 
arches,  piers  and  abutments  and  the  low- 
er  6  ins.  of  the  inner  surface  of  the 
spandrel  walls  shall  be  coated  with  a 
heavy  coat  of  semi-liquid  mortar  con- 
sisting  of  1  part  cement,  J/2  part  thor- 
oughly  slaked  lime  and  3  parts  sand, 
spread  to  leave  a  smooth  finish,  and 
after  this  has  set  hard  it  shall  be  given  a 
heavy  coat  of  puré  cement  grout. 

Fill. — The  space  between  the  spandrel 
walls  shall  be  filled  with  sand,  earth,  cin- 
ders  or  other  suitable  material,  thor- 
oughly  compacted  by  ramming  or  roll- 
ing,  and  be  finished  to  the  proper  grade 
to  receive  the  curbing  and  pavement. 
The  fill  over  any  arch  shall  not  be  put  in 
until  at  least  two  weeks  after  the  arch 
concrete  has  been  completed. 

SPECIFICATIONS        FOR        SIDE- 
WALKS.* 

Materials. — The  cement  shall  meet  the 
requirements  of  the  specifications  for 
Portland  cement  of  the  American  Socie- 
ty  for  Testing  Materials  and  adopted  by 
this  association  (Standard  No.  1)  Janu- 
ary,  1906. 

Aggregates. — Fine  aggregate  shall  con- 
sist  of  sand,  crushed  stone,  or  gravel 
screenings,   graded   from   fine   to   coarse, 


^Standard  specifications  adopted  by  the 
National  Association  of  Cement  Users,  Jan- 
uary,  1908.     Revised  Januarv,  1909. 


bfEUMLATlONS.  W¿ 

passing  when  dry  a  screen  having  *4-in. 
diameter  holes,  shall  be  preferably  of 
silicious  materials,  clean,  coarse,  free 
from  vegetable  loam  or  other  deleterious 
matter,  and  not  more  than  6  per  cent 
shall  pass  a  sieve  having  100  meshes  per 
linear  inch. 

Mortars  composed  of  one  part  Port- 
land  cement  and  three  parts  fine  aggre- 
gate  by  weight  when  made  into  briquets 
shall  show  a  tensile  strength  of  at  least 
70  per  cent  of  the  strength  of  1:3  mortar 
of  the  same  consistency  made  with  the 
same  cement  and  standard  Ottawa  sand. 

Coarse  aggregate  shall  consist  of  inert 
material,  graded  in  size,  such  as  crushed 
stone  or  gravel,  which  is  retained  on  a 
screen  having  %-in.  diameter  holes,  shall 
be  clean,  hard,  durable,  and  free  from  all 
deleterious  materials.  Aggregates  con- 
taining  soft,  fíat  or  elongated  particles 
shall  be  excluded. 

The  máximum  size  of  the  coarse  ag- 
gregate shall  be  such  that  it  will  not  sep- 
árate from  the  mortar  in  laying  and  will 
not  prevent  the  concrete  fully  filling  all 
parts  of  the  forms.  The  size  of  the 
coarse  aggregate  shall  be  such  as  to  pass 
a  1^-in.  ring. 

Water  shall  be  clean,  free  from  oil, 
acid,  strong  alkalies  or  vegetable  matter. 

Forms. — Forms  shall  be  free  from 
warp  and  of  sumcient  strength  to  resist 


144  CONCRETE    INSPECTION. 

springing  out  of  shape.  All  mortar  and 
dirt  shall  be  removed  from  forms  that 
have  been  previously  used. 

The  forms  shall  be  well  staked  to  the 
established  lines  and  grades,  and  their 
upper  edges  shall  conform  with  finished 
grade  of  the  walk,  which  shall  have  suffi- 
cient  rise  from  the  curb  to  provide  prop- 
er  drainage;  but  this  rise  shall  nc  ex- 
ceed  three-eighths  (fá)  of  an  inch  per 
foot,  except  where  such  rise  shall  paral- 
lel  the  length  of  the  walk. 

All  forms  shall  be  thoroughly  wetted 
before  any  material  is  deposited  against 
them. 

Size  and  Thickness  of  Slabs. — Slabs 
without  reinforcement  shall  not  contain 
more  than  36  square  feet  or  have  any  di- 
mensión greater  than  6  feet.  For  great- 
er  área,  slabs  shall  be  reinforced  with 
one-quarter  (J4)  mch  Steel  rods,  not 
more  than  nine  (9)  inches  apart,  or  oth- 
er  reinforcement  equally  as  strong. 

The  mínimum  thickness  of  the  pave- 
ment  shall  not  be  less  than  four  (4) 
inches. 

Sub-Base.— The  sub-base  shall  be 
thoroughly  rammed,  and  all  soft  spots 
removed  and  replaced  by  some  suitable 
hard  material. 

When  a  fill  exceeding  one  foot  in 
thickness  is  required,  it  shall  be  thor- 
oughly compacted  by  flooding  and  tamp- 


SPEC1FICA  TIONS.  145 

ing  in  layers  of  not  exceeding  six  (6) 
inches  in  thickness,  and  shall  have  a 
slope  of  not  less  than  one  to  one  and  a 
half  (1:1JÍ). 

The  top  of  all  filis  shall  extend  at 
least  12  inches  beyond  the  sidewalk. 

While  compacting,  the  sub-base  shall 
be  thoroughly  wetted  and  shall  be  main- 
taineJ  in  that  condition  until  the  con- 
crete is  deposited. 

Base. — The  concrete  for  the  base  shall 
be  so  proportioned  that  the  cement  shall 
overfill  the  voids*  in  the  fine  aggregate 
by  at  least  five  (5)  per  cent,  and  the 
mortar  shall  overfill  the  voids  in  the 
coarse  aggregate  by  at  least  ten  (10)  per 
cent.  The  proportions  shall  not  exceed 
one  (1)  part  of  cement  to  eight  (8)  parts 
of  fine  or  coarse  aggregates. 

When   the   voids   are   not    determined, 

*To  determine  voids,  fill  a  vessel  with  sand  and  let 
net  weight  of  sand  equal  B.  Fill  same  vessel  with 
water  and  let  net  weight  of  water  equal  A. 

B  .,       A  X  2.65-B     1ft_ 

Per  cent  voids  ■      .  -  =  _,    X  100 
A  X  ¿.o5 

This  formula  may  also  be  used  in  determining  voids 
in  crushed  stone  and  screenings  by  substituting  for 
2.65  the  specific  gravity  of  the  stone  . 

The  following  is  a  more  simple  method  for  deter- 
mining voids  in  coarse  aggregate.  Fill  a  vessel  with 
the  aggregate  and  let  net  weight  equal  B.  Add  water 
slowly  until  it  just  appears  on  the  surface  and  weigh. 
Let  net  weight  equal  A .  Fill  same  vessel  with  water 
and  let  net  weight  equal  C . 

A—B 
Per  cent  voids  =— -^-XlOO 

Use  a  vessel  of  not  less  than  one-half  (£)  cubic  foot 
capacity.  The  larger  the  vessel  the  more  accurate 
the  result. 


146  CONCRETE    1NSPEC110N. 

the  concrete  shall  have  the  proportions 
of  one  (1)  part  cement,  three  (3)  parts 
fine  aggregates  and  five  (5)  parts  coarse 
aggregates.  A  sack  of  cement  (94 
pounds)  shall  be  considered  to  have  a 
volume  of  one  (1)  cubic  foot. 

Mixing. — The  ingredients  of  concrete 
shall  be  thoroughly  mixed  to  the  de- 
sired  consistency,  and  the  mixing  shall 
continué  until  the  cement  is  uniformly 
distributed  and  the  mass  is  uniform  in 
color  and  homogeneous. 

a.  Measuring  Proportions. — Methods 
of  measurement  of  the  proportions  of 
the  various  ingredients  including  the  wa- 
ter shall  be  used  which  will  secure  sep- 
árate uniform  measurements  at  all  times. 

b.  Machine  Mixing. — When  the  condi- 
tions  will  permit,  a  machine  mixer  of  a 
type  which  insures  the  proper  mixing  of 
the  materials  throughout  the  mass  shall 
be  used. 

c.  Hand  Mixing. — When  it  is  necessary 
to  mix  by  hand,  the  mixing  shall  be  on  a 
water-tight  platform  and  the  materials 
shall  be  turned  until  they  are  homoge- 
neous in  appearance  and  color. 

d.  Consistency. — The  materials  shall 
be  mixed  wet  enough  to  produce  a  con- 
crete of  such  a  consistency  as  will  flush 
readily  under  light  tamping  and  which, 
on  the  other  hand,  can  be  conveyed  from 
the  mixer  to  the  forms  without  separa- 


SPECIFICA  TIONS.  147 

tion  of  the  coarse  aggregate  from  the 
mortar. 

e.  Retempering. — Retempering  mortar 
or  concrete — i.  e.,  remixing  with  water 
after  it  has  partially  set — shall  not  be 
permitted. 

Placing  of  Concrete. — a.  Methods. — 
After  the  addition  of  water  the  mix  shall 
be  handled  rapidly  to  the  place  of  final 
deposit,  and  under  no  circnmstances 
shall  concrete  be  used  that  has  partially 
set. 

b.  Freezing  Weather. — The  concrete 
shall  not  be  mixed  or  deposited  at  a 
freezing  temperatnre  unless  special  pre- 
cautions  are  taken  to  avoid  the  use  of 
materials  containing  frost  or  covered 
with  ice  crystals,  and  in  providing  means 
to  prevent  the  concrete  from  freezing 
after  being  placed  in  position  and  until  it 
has  thoroughly  hardened. 

Sidewalks  shall  be  laid  in  such  a  man- 
ner  as  to  insure  the  protection  of  the 
pavement  from  injury  due  to  changes  in 
foundations  or  from  contraction  and  ex- 
pansión. 

Workmen  shall  not  be  permitted  to 
walk  on  freshly  laid  concrete,  and  where 
sand  or  dust  collects  on  the  base  it  shall 
be  carefully  removed  before  the  wearing 
surface  is  applied. 

Wearing  Surface. — The  wearing  course 
shall  have  a  thickness  of  at  least  one  (1) 
inch. 


148  CONCRETE   INSPECTION. 

The  wearíng  surface  shall  be  mixed  in 
the  same  manner  as  the  mortar  for  the 
base,  the  proportion  one  (1)  cement  to 
two  (2)  of  fine  aggregate,  and  it  shall  be 
of  such  consistency  as  will  not  require 
tamping,  but  will  be  readily  floated  with 
a  straight  edge. 

The  wearing  surface  shall  be  spread 
on  the  base  immediately  after  mixing, 
and  in  no  case  shall  more  than  fifty  (50) 
minutes  elapse  between  the  time  that  the 
concrete  for  the  base  is  mixed  and  the 
time  that  the  wearing  course  is  floated. 

After  being  worked  to  an  approxi- 
mately  true  surface,  the  slab  markings 
shall  be  made  directly  over  the  joints  in 
the  base  with  a  tool  which  shall  cut  clear 
through  to  the  base  and  completely  sep- 
árate the  wearing  courses  of  adjacent 
slabs. 

The  slabs  shall  be  rounded  on  all  sur- 
face  edges  to  a  radius  of  not  less  than 
one-half   {]/2)   inch. 

When  required,  the  surface  shall  be 
troweled  smooth. 

The  application  of  neat  cement  to  the 
surface  in  order  to  hasten  the  hardening 
is  prohibited. 

On  grades  exceeding  five  (5)  per  cent 
the  surface  shall  be  roughened.  This 
may  be  done  by  the  use  of  a  grooving 
tool,  toothed  roller,  brush,  wooden  float 
or    other   suitable   tool,    or   by   working 


SPECIFICATIONS.  149 

coarse  sand  or  screenings  into  the  sur- 
face. 

Where  color  is  used  it  shall  be  incor- 
porated  uniformly  and  the  quantity  and 
quality  shall  be  such  as  to  not  impair  the 
strength  of  the  wearing  surface. 

Single  Coat  Work. — Single  coat  work 
shall  be  composed  of  one  part  of  cem- 
ent,  two  parts  of  fine  aggregate  and 
three  parts  of  coarse  aggregate,  and  the 
slabs  separated  as  provided  for  in  the 
specifications  for  two  coat  work. 

The  concrete  shall  be  firmly  compact- 
cd  by  tamping  and  evenly  struck  off  and 
smoothed  to  the  top  of  the  form.  Then 
with  a  suitable  tool  the  coarser  particles 
of  the  concrete  shall  be  tamped  to  a 
depth  which  will  permit  of  finishing  the 
walk  as  under  "Wearing  Surface. " 

Protection  and  Grading. — When  com- 
pleted,  the  walk  shall  be  kept  moist  and  i 
protected  from  traffic  and  the   elements 
for  at  least  three  days. 

Grading  after  the  walks  are  ready  for 
use  should  be  on  the  curb  side  of  the 
sidewalk,  one  and  one-half  (lyí)  inches 
lower  than  the  sidewalk,  and  not  less 
than  one-quarter  (%)  inch  to  the  foot 
fall  towards  the  curb  or  gutter.  On  the 
property  side  of  the  walk  the  ground 
should  be  graded  back  at  least  two  (2) 
feet  and  not  lower  than  the  walk;  this 


150  CONCRETE    1NSPECT10N. 

will   insure   the   frost   throwing  the  walk 
alike  on  both  sides. 

Curbs. — The  trench  shall  be  excavated 
to  a  depth  not  greater  than  the  bottom 
of  the  curb  and  a  width  not  greater  than 
the  thickness  of  the  curb  plus  six  (6) 
inches. 

The  thickness  of  the  curb  shall  not  be 
less  than  six  (6)  inches. 

After  the  forms  are  set  about  one  (1) 
inch  of  wearing  surface  shall  be  placed 
on  the  inside  of  the  curb  form,  then  the 
concrete  shall  be  deposited  at  one  op- 
eration  and  firmly  tamped  to  within  one 
(1)  inch  of  the  top  of  forms.  The  top 
wearing  surface  shall  then  be  placed  and 
be  of  the  same  composition  as  that 
specified  for  sidewalks. 

Joints  shall  be  made  three-fourths  (¿4) 
the  depth  of  the  curb,  continuous  with 
joints  of  the  sidewalk  and  in  no  case 
more  than  six  (6)   feet  apart. 

The  forms  shall  be  removed  as  soon 
as  practical  and  the  faces  finished  at  one 
operation,  floating  down  six  (6)  inches 
with  a  one  to  one  mixture  of  cement  and 
fine  aggregate  of  sufiicient  thickness  to 
produce  a  smooth  surface. 

Where  a  combination  curb  and  gutter 
is  required,  they  shall  be  cast  at  the 
same  time  and  finished  at  one  operation- 


SPECIFICATIONS.  151 

SPECIFICATIONS  FOR  HOLLOW 
BUILDING  BLOCKS.* 

Regulations  Governing  Use  and  Man- 
ufacture.— Hollow  cement  blocks  made 
in  accordance  with  the  following  specifi- 
cations  and  meeting  the  requirements 
thereof  may  be  tised  in  building  con- 
struction,  subject  to  the  usual  form  of 
approval,  required  of  other  materials  of 
construction,  by  the  bureau  of  building 
inspection. 

The  cement  used  in  making  blocks 
shall  be  Portland  cement,  capable  of 
passing  the  requirements  as  set  forth  in 
the  "Standard  Specifications  for  Cem- 
ent," of  the  American  Society  for  Test- 
ing  Materials,  and  adopted  by  this  asso- 
ciation   (Standard  .No.   1)   January,   1906. 

The  sand  used  shall  be  suitable  siliceous 
material,  passing  the  one-fourth  inch 
mesh  sieve,  clean,  gritty  and  free  from 
impurities. 

This  material  shall  be  clean  broken 
stone,  free  from  dust,  or  clean  screened 
gravel  passing  the  three-quarter  (¿4) 
inch,  and  refused  by  the  one-quarter 
(%)  inch,  mesh  sieve. 

The  barrel  of  Portland  cement  shall 
weigh  380  pounds  net,  either  in  barréis 
or    sub-divisions  thereof,  made  up  of  cloth 


♦Standard  specifications  adopted  by  the 
National  Cement  Users  Association,  January, 
1908.     Revised  January,  1909. 


152  CONCRETE    INSPECTION. 

or  paper  bags,  and  a  cubic  foot  of  cem- 
ent  shall  be  called  not  to  exceed  100 
pounds  or  the  equivalent  of  3.8  cubic 
feet  per  barrel.  Cement  shall  be  gauged 
or  measured  either  in  the  original  pack- 
age  as  received  from  the  manufacturer 
or  may  be  weighed  and  so  proportioned; 
but  under  no  circumstances  shall  it  be 
measured  loóse  in  bulk. 

For  exposed  exterior  or  bearing  walls. 

(a)  Hollow  cement  blocks,  machine 
made,  using  semi-wet  concrete  or  mor- 
tar,  shall  contain  one  (1)  part  cement, 
not  to  exceed  three  (3)  parts  sand  and 
not  to  exceed  four  (4)  parts  stone  of  the 
character  and  size  before  stipulated. 
When  the  stone  shall  be  omitted  the 
proportions  of  sand  shall  not  be  in-' 
creased,  unless  it  can  be  demonstrated 
that  the  percentage  of  voids  and  tests  of 
absorptiqn  and  strength  allow  in  each 
case  of  greater  proportions  with  equally 
good  results. 

(b)  When  said  blocks  are  made  of 
slush  concrete,  in  individual  molds,  and 
allowed  to  harden  undisturbed  in  same 
before  removal,  the  proportions  may  be 
one  (1)  part  cement,  not  to  exceed  three 
(3)  parts  sand  and  five  (5)  parts  stone, 
but  in  this  case  also,  if  the  stone  be 
omitted  the  proportion  of  sand  shall  not 
be  increased. 

Thorough  and  vigorous  mixing  is  of 
the  utmost  importance. 


SPECIFICATIONS.  153 

(a)  Hand  Mixing.-^The  cement  and 
sand  in  correct  proportions  shall  first  be 
perfectly  mixed  dry,  the  water  shall  then 
be  added  carefully  and  slowíy  in  proper 
proportions  and  thoroughly  worked  into 
and  throughout  the  resultant  mortar;  the 
moistened  gravel  or  broken  stone  shall 
then  be  added,  either  by  spreading  the 
same  uniformly  over  the  mortar  or 
spreading  the  mortar  uniformly  over  the 
stones,  and  then  the  whole  mass  shall  be 
vigorously  mixed  together  until  the 
coarse  aggregate  is  thoroughly  incor- 
porated  with  and  distributed  throughout 
the  mortar. 

(b)  Machine  Mixing. — Preference  shall 
be  given  to  machine  mixers  of  suitable 
design  and  adapted  to  the  particular 
work  required  of  them;  the  sand  and 
cement  or  sand  and  cement  and  moist- 
ened stone  shall,  however,  be  first  thor- 
oughly mixed  before  the  addition  of  wa- 
ter, and  then  continued  until  the  water  is 
uniformly  distributed  or  incorporated 
with  the  mortar  or  concrete;  provided, 
however,  that  when  making  slush  or  wet 
concrete  (such  as  will  quake  or  flow) 
this  procedure  may  be  varied  with  the 
consent  of  the  bureau  of  building  inspec- 
tion,  architect  or  engineer  in  charge. 

Due  care  shall  be  used  to  secure  dertsi- 
ty  and  uniformity  in  the  blocks  by  tamp- 
ing  or  other  suitable  means  of  compres- 
sion.     Tamped   blocks   shall   not  be   fin- 


154  CONCRETE   INSPECTION. 

ished  by  simply  striking  ofí  with  a 
straight  edge,  but,  after  striking  ofí,  the 
top  surfaces  shall  be  trowelled  or  other- 
wise  finished  to  secure  density  and  a 
sharp  and  true  arris. 

Every  precaution  shall  be  taken  to 
prevent  the  drying  out  of  the  blocks  dur- 
ing  their  initial  set  and  first  hardening. 
A  sufíiciency  of  water  shall  first  be  used 
in  the  mixing  to  perfect  the  crystalliza- 
tion  of  the  cement,  and,  after  molding, 
the  blocks  shall  be  carefully  protected 
from  wind  currents,  sunlight,  dry  heat 
or  freezing  for  at  least  five  (5)  days, 
during  which  time  additional  moisture 
shall  be  supplied  by  approved  methods, 
and  occasionally  thereafter  until  ready 
for  use. 

Hollow  cement  blocks  in  which  the 
ratio  of  cement  to  sand  be  one-third  (l/y) 
(one  part  cement  to  three  parts  sand) 
shall  not  be  used  in  the  construction  of 
any  building  until  they  have  attained  the 
age  of  not  less  than  three  (3)  weeks. 

„  Hollow  cement  blocks  in  which  the 
ratio  of  cement  to  sand  be  one-half  (l/2) 
(one  part  cement  to  two  parts  sand) 
may  be  used  in  construction  at  the  age 
of  two  (2)  weeks,  with  the  special  con- 
sent  of  the  bureau  of  building  inspection 
and  the  architect  or  engineer  in  charge. 
Special  blocks  of  rich  composition,  re- 
quired  for  closures,  may  be  use<J  at  the 


SPECIFICATIONS.  155 

age  of  seven  (7)  days  with  the  special 
Lonsent  of  the  same  authorities. 

The  time  herein  named  is  conditional, 
however,  upon  maintaining  proper  con- 
ditions  of  exposure  during  the  curing 
period. 

All  cement  blocks  shall  be  marked,  for 
purposes  of  identification,  showing  ñame 
of  manufacturer  or  brand,  date  (day, 
month  and  year)  made,  and  composition 
or  proportions  used,  as,  for  example, 
1 — 3 — 5,  meaning  one  cement,  three  sand 
and  five  stone. 

The  thickness  of  bearing  walls  for  any 
building  where  hollow  cement  blocks  are 
used  may  be  ten  (10)  per  cent  less  than 
is  required  by  law  for  brick  walls.  For 
curtain  walls  or  partition  walls,  the  re- 
quirements  shall  be  the  same  as  in  the 
use  of  hollow  tile,  térra  cotta  or  plaster 
blocks. 

Hollow  cement  blocks  shall  not  be 
permitted  in  the  construction  of  party 
walls,  except  when  filled  solid. 

Where  the  face  only  is  of  hollow  cem- 
ent block  and  the  backing  is  of  brick,  the 
facing  of  hollow  block  must  be  strongly 
bonded  to  the  brick,  either  with  headers 
projecting  four  (4)  inches  into  the  brick 
work,  every  fourth  course  being  a  head- 
er  course,  or  with  approved  ties,  no 
brick  backing  to  be  less  than  eight  (8) 
inches.  Where  the  walls  are  made  en- 
tirely  of  concrete  blocks,  but  where  said 


156  CONCRETE    1NSPECTI0N. 

blocks  have  not  the  same  width  as  the 
wall,  every  fifth  course  shall  extend 
through  the  wall,  forming  a  secure  bond, 
when  not  otherwise  sufficiently  bonded. 
All  walls,  where  blocks  are  used,  shall  be 
laid  up  with  Portland  cement  mortar. 

Wherever  girders  or  joists  rest  npon 
walls  so  that  there  is  a  concentrated  load 
on  the  block  of  over  two  (2)  tons,  the 
blocks  supporting  the  girder  or  joists 
must  be  made  solid  for  at  least  eight  (8) 
inches  from  the  inside  face.  Where  such 
concentrated  load  shall  exceed  five  (5) 
tons,  the  blocks  for  at  least  three  courses 
below  and  for  a  distance  extending  at 
least  eighteen  (18)  inches  each  side  of 
said  girder,  shall  be  made  solid  for  at 
least  eight  (8)  inches  from  the  inside 
face.  Wherever  walls  are  decreased  in 
thickness,  the  top  course  of  the  thicker 
wall  shall  afford  a  full  solid  bearing  for 
the  webs  or  walls  of  the  course  of  blocks 
above. 

No  wall  ñor  any  part  thereof  com- 
posed  of  hollow  cement  blocks  shall  be 
loaded  to  an  ex-cess  of  eight  (8)  tons  per 
superficial  foot  of  the  área  of  such  blocks, 
including  the  weight  of  the  wall,  and  no 
blocks  shall  be  used  in  bearing  walls 
that  have  an  average  crushing  strength 
of  less  than  1,000  lbs.  per  square  inch  of 
área  at  the  age  of  twenty-eight  (28) 
days;  no  deduction  to  be  made  in  figur- 
ing  the  área  for  the  hollow  spaces.     . . 


SPECIFICA  TIONS.  157 

Concrete  sills  and  lintels  shall  be  rein- 
forced  by  iron  or  steel  rods  in  a  rnanner 
satisfactory  to  the  bureau  of  building  in- 
spection  and  the  architect  or  engineer  in 
charge,  and  any  lintels  spanning  over  4 
feet  6  inches  shall  rest  on  block  solid  for 
at  least  8  inches  from  the  face  next  the 
opening  and  for  at  least  three  courses 
below  the  bottom  of  the  lintel. 

The  hollow  space  in  building  blocks 
used  in  bearing  walls  shall  not  exceed 
the  percentage  given  in  the  following  ta- 
ble  of  different  height  walls,  except 
where  blocks  containing  a  greater  per- 
centage shall  be  proven  by  actual  test  to 
meet  all  the  test  requirements  herein 
specified  to  the  satisfaction  of  the  bu- 
reau of  building  inspection,  and  in  no 
case  shall  the  walls  or  webs  of  the  block 
be  less  in  thickness  than  one-fourth  their 
height.  The  figures  given  in  the  table 
represent  the  percentage  of  such  hollow 
space  for  different  height  walls: 


Stories 

lst 

2d 

3d 

4th  5th  6th 

1  and  2 

33 

33 

3  and  4 

25 

33 

33 

33 

5  and  6 

20 

25 

25 

33  33    33 

Before  any  such  material  be  used  in 
buildings,  an  application  for  its  use  and 
for  a  test  of  the  same  must  be  filed  with 
the  bureau  of  building  inspection.  In  the 
absence  of  such  a  bureau,  the  application 
shall  be  filed  with  the  chief  of  any  de- 


158  CONCRETE   INSPECTION. 

partment  having  such  matters  in  charge. 
A  description  of  the  material  and  a  brief 
outline  of  its  manufacture  and  propor- 
tions  used  must  be  embodied  in  the  ap- 
plication.  The  ñame  of  the  firm  or  Cor- 
poration and  the  responsible  officers 
thereof  shall  also  be  given,  and  changes 
in  same  thereafter  promptly  reported. 

No  hollow  cement  blocks  shall  be  used 
in  the  construction  of  any  building  un- 
less  the  maker  of  said  blocks  has  sub- 
mitted  his  product  to  the  full  tests  re- 
quired  herein,  and  placed  on  file  with 
the  bureau  of  building  inspection  or 
other  duly  authorized  omcial  a  certifí- 
cate from  a  reliable  testing  laboratory 
showing  that  representative  samples 
have  been  tested  and  successfully  passed 
all  the  requirements  hereof,  and  giving 
in  detail  the  results  of  the  tests  made. 

No  cement  blocks  shall  be  used  in  the 
construction  of  any  building  until  they 
have  been  inspected  and  approved,  or,  if 
rcquired,  until  representative  samples  be 
tested  and  found  satisfactory.  The  re- 
sults of  all  tests  made,  whether  satisfac- 
tory or  not,  shall  be  placed  on  file  in  the 
bureau  of  building  inspection.  These 
records  shall  be  open  to  inspection  upon 
application,  but  need  not  necessarily  be 
published. 

The  manufacturer  and  user  of  such 
hollow  cement  blocks,  or  either  of  them, 


SPECIFICATIONS.  159 

shall  at  any  and  all  times  have  made 
such  tests  of  the  cements  used  in  mak- 
ing  such  blocks  or  such  further  tests  of 
the  completed  blocks  or  of  each  of 
these,  at  their  own  expense  and  under 
the  supervisión  of  the  bureau  of  building 
inspection,  as  the  chief  of  said  bureau 
shall  require. 

In  case  the  result  of  tests  made  under 
this  condition  should  show  that  the 
standard  of  these  regulations  is  not 
maintained,  the  certifícate  of  approval 
issued  to  the  manufacturer  of  said  blocks 
will  at  once  be  suspended  or  revoked. 

Following  the  application  called  for  in 
clause  No.  18  and  upon  the  satisfactory 
conclusión  of  the  tests  called  for,  a  cer- 
tifícate of  approval  shall  be  issued  to  the 
maker  of  the  blocks  by  the  bureau  of 
building  inspection.  This  certifícate  of 
approval  will  not  remain  in  forcé  for 
more  than  four  months,  unless  there  be 
filed  with  the  bureau  of  building  inspec- 
tion, at  least  once  every  four  months  fol- 
lowing, a  certifícate  from  some  reliable 
physical  testing  laboratory  showing  that 
the  average  of  at  least  three  (3)  speci- 
mens  tested  for  compression  and  at  least 
three  (3)  specimens  tested  for  transverse 
strength  comply  with  the  requirements 
herein  set  forth,  the  said  samples  to  be 
selected  by  a  building  inspector  or  by 
the  laboratory  from  blocks  actually  go- 
ing  into  construction  work. 


160  CONCRETE    INSPECTICN. 

Hollow  cement  blocks  mnst  be  sub- 
jected  to  the  following  tests,  transverse, 
compression  and  absorption,  and  may  be 
subjected  to  the  freezing  and  fire  tests, 
but  the  expense  of  conducting  the  freez- 
ing and  fire  tests  will  not  be  imposed 
upon  the  manufacturer  of  said  blocks. 

The  test  samples  must  represent  the 
ordinary  commercial  product,  of  the  reg- 
ular size  and  shape  used  in  construction. 
The  samples  may  be  tested  as  soon  as 
desired  by  the  applicant,  but  in  no  case 
later  than  sixty  days  after  manufacture. 
Transverse  Test. — The  modulus  of  rup- 
ture  for  concrete  blocks  at  twenty-eight 
days  must  average  150,  and  must  not  fall 
below  100  in  any  case. 

Compression  Test. — The  ultímate  com- 
pressive  strength  at  twenty-eight  days 
must  average  one  thousand  (1,000) 
pounds  per  square  inch,  and  must  not 
fall  below  700  in  any  case. 

Absorption  Test. — The  percentage  of 
absorption  (being  the  weight  of  water 
absorbed  divided  by  the  weight  of  the 
dry  sample)  must  not  average  higher 
than  15  per  cent,  and  must  not  exceed  22 
per  cent  in  any  case. 

Any  and  all  blocks,  samples  of  which, 
on  being  tested  under  the  direction  of 
the  bureau  of  building  inspection,  fail  to 
stand  at  twenty-eight  (28)  days  the  tests 
required    by    this    regulation     shall     be 


SPEC1F1CA  TIONS.  161 

marked    "condemned"    by   the   manufac- 
turer  or  user  and  shall  be  destroyed. 

Cement  brick  may  be  used  as  a  substi- 
tute  for  clay  brick.  They  shall  be  made 
of  one  part  cement  to  not  exceeding  four 
parts  clean  sharp  sand,  or  one  part  cem- 
ent to  not  exceeding  three  parts.  clean 
sharp  sand  and  three  parts  broken  stone 
or  gravel  passing  the  H~inch  and  re- 
fused  by  the  54-inch  mesh  sieve.  In  all 
other  respects  cement  brick  must  con- 
form  to  the  requirements  of  the  fore- 
going  specifications. 

Standard   Method   of  Testing.— 1.    All 

tests  required  for  approval  shall  be  made 
in  some  laboratory  of  recognized  stand- 
ing,  under  the  supervisión  of  the  engi- 
neer  of  the  bureau  of  building  inspec- 
tion  or  the  architect  or  engineer  in 
charge,  or  all  of  these.  The  manufactur- 
er  may  be  present  or  represented  during 
said  tests,  if  he  so  desires.  Approval  , 
tests  are  made  at  the  expense  of  the 
applicant. 

2.  For  the  purposes  of  the  tests,  at 
least  twelve  (12)  samples  or  test  pieces 
must  be  provided.  Such  samples  must 
represent  the  ordinary  commercial  prod- 
uct  and  may  be  selected  from  stock  by 
the  bureau  of  building  inspection  or,  in 
the  absence  of  such  a  bureau,  by  the 
architect  or  engineer  in  charge. 

In   cases  where   the  material   is  made 


162  CONCRETE    INSPECTION. 

and  used  in  special  shapes  or  forms,  too 
large  for  testing  in  the  ordinary  ma- 
chines, smaller  sized  specimens  shall  be 
used  as  may  be  directed. 

3.  In  addition  to  the  tests  required  for 
approval,  the  weight  per  cubic  foot  of 
the  material  must  also  be  obtained  and 
recorded. 

4.  Tests  shall  be  made  in  series  of  at 
least  three  (3),  except  that  in  the  fire 
tests  a  series  of  two  (four  samples)  are 
sumcient. 

Transverse  tests  shall  be  made  on  full 
sized  samples.  Half  samples  may  be 
used  for  the  crushing,  freezing  and  fire 
tests.  The  remaining  samples  are  kept 
in  reserve,  in  case  duplicate  or  confirma- 
tory  tests  be  required.  All  samples  must 
be  marked  for  identification  and  com- 
parison. 

5.  The  transverse  test  shall  be  made 
as  follows:  The  samples  shall  be  placed 
flatwise  on  two  rounded  knife  edge  bear- 
ings  set  parallel  7  inches  apart.  A  load 
is  then  applied  on  top,  midway  between 
the  supports,  and  transmitted  through  a 
similar  rounded  knife  edge,  until  the 
sample  is  ruptured.  The  modulus  of 
rupture  shall  then  be  determined  by  mul- 
tiplying  the  total  breaking  load  in 
pounds  by  21  (three  times  the  distance 
between  supports  in  inches)  and  then  di- 
viding  the  result  thus  obtained  by  twice 


SPEC1FICATI0NS.  163 

the  product  of  the  width  in  inches  by  the 

3w/ 

square  of  the  depth  in  inches.     R  = 

2bd" 

No  allowance  should  be  made  in  figuring 

the  modulus   of   rupture   for  the   hollow 

spaces. 

6.  The  compression  test  shall  be  made 
as  follows:  Samples  must  be  cut  from 
blocks,  so  as  to  contain  a  full  web  sec- 
tion.  The  sample  must  be  carefully 
measured,  then  bedded  flatwise  in  plas- 
ter  of  Paris,  to  secure  a  uniform  bearing 
in  the  testing  machine,  and  crushed.  The 
total  breaking  load  is  then  divided  by 
the  área  in  compression  in  square  inches, 
no  deduction  to  be  made  for  hollow 
spaces;  the  área  will  be  considered  as 
the  product  of  the  width  by  the  length. 

7.  The  absorption  test  shall  be  made 
as  follows:  The  sample  is  first  thorough- 
ly  dried  to  a  constant  weight,  at  not  to 
exceed  212°  F.  The  weight  must  be  * 
carefully  recorded.  It  is  then  placed  in 
a  pan  or  tray  of  water,  face  downward, 
immersing  it  to  a  depth  of  not  less  than 

2  inches.  It  is  again  carefully  weighed 
at  the  following  periods:  Thirty  minutes, 
four  hours,  and  forty-eight  hours,  re- 
spectively,  from  the  time  of  immersion, 
being  replaced  in  the  water  in  each  case 
as  soon  as  the  weight  is  taken.  Its  com- 
prehensive  strength,  while  still  wet,  is 
then  determined  at  the  end  of  the  forty- 


164  CONCRETE    INSPECTION. 

eight  hours'  period,  in  the  manner  speci- 
fied  in  Section  6. 

8.  The  freezing  test  shall  be  made  as 
follows:  The  sample  is  immersed,  as  de- 
scribed  in  Section  7,  for  at  least  four 
hours,  and  then  weighed.  It  is  then 
placed  in  a  freezing  mixture  ora  refrig- 
erator,  or  otherwise  subjected  to  a  tem- 
perature  of  less  than  15°  F.  for  at  least 
twelve  hours.  It  is  then  removed  and 
placed  in  water,  where  it  must  remain 
for  at  least  one  hour,  the  temperature  of 
which  is  at  least  150°  F.  This  operation 
is  repeated  ten  (10)  times,  after  which 
the  sample  is  again  weighed  while  still 
wet  from  the  last  thawing.  Its  crushing 
strength  should  then  be  determined,  as 
called  for  in  Section  6. 

9.  The  fire  test  is  made  as  follows: 
Two  samples  are  placed  in  a  cold  fur- 
nace  in  which  the  temperature  is  grad- 
ually  raised  to  1700°  F.  The  test  piece 
must  be  subjected  to  this  temperature 
for  at  least  thirty  minutes.  One  of  the 
samples  is  then  plunged  in  cold  water 
(about  50°  to  60°  F.)  and  the  results 
noted.  The  second  sample  is  permitted 
to  cool  gradually  in  air,  and  the  result 
noted. 

10.  The  following  requirements  must 
be  met  to  secure  an  acceptance  of  the 
materials:  The  modulus  of  rupture  for 
concrete  blocks  at  twenty-eight  days 
must  average  150,  and  must  not  fall  be- 


SPECIFICATIONS.  *  165 

low  100  in  any  case.  The  ultímate  com- 
pressive  strength  at  twenty-eight  days 
must  average  1,000  pounds  per  square 
inch,  and  must  not  fall  below  700  in  any 
case.  The  percentage  of  absorption  (be- 
ing  the  weight  of  water  absorbed  divided 
by  the  weight  of  the  dry  sample)  must 
not  average  higher  than  15  per  cent  and 
must  not  exceed  22  per  cent  in  any  case. 
The  reduction  of  compressive  strength 
must  not  be  more  than  33^  per  cent,  ex- 
cept  that  when  the  lower  figure  is  still 
above  1,000  pounds  per  square  inch  the 
loss  in  strength  may  be  neglected.  The 
freezing  and  thawing  process  must  not 
cause  a  loss  in  weight  greater  than  10 
per  cent  ñor  a  loss  in  strength  of  more 
than  33*/3  per  cent,  except  that  when  the 
lower  figure  is  still  above  1,000  pounds 
per  square  inch,  the  loss  in  strength  may 
be  neglected.  The  fire  test  must  not 
cause  the  material  to  disintegrate. 


INDEX. 

Page 
Aeid   Wash,    Bonding    New    Concrete    to 

Oíd     56,     78 

Finishing     Surfaces     With,     Directions 

for     70 

Aggregates,    Broken    Stone,    Best    Rocks 

for    12,  106 

Burnt  Clay,  Character  and  Composition 

Required     106 

Cinders,    Character     and     Composition 

Required     13,  115 

Cleanliness    Required    14,  133 

Density    Proportions    Required 100 

Determinations  Usually   Required 14 

Gravel,  Merits  of  for  Concrete 13 

Materials,  Kinds  of  Used  for.. 12,  95,  115,  153 

Properties   Usually    Specified 13 

Sizes    of    95,  96,  106,  116,  142 

Slag,   Kind  and  Composition  Required.     13 

Voids  in,  Determination   of 11,  14,  145 

Alignment    of    Forms 27,111 

Alkali  Water  15 

Arch  Centers,  Construction,  Directions.34,  141 

Removing,    Time    for 36 

Striking,  Directions  for 37,  141 

Provisions    for    34,  141 

Arches,      Concreting      See      "Concreting 
A.rches  " 

Drainage,    Directions    for 60,  137 

Filling  Over,   Directions  for 60,142 

Reinforcing         See  "Reinforcement         * 

Arches." 

Ring  Sections,  Forms  for 34 

Spandrels,   Thickness  of 136 

Artificial  Heaters,  Directions  for  Using..     66 
Automatic  Measuring  Devices,  Control  of    20 
Bags,    Subaqueous   Concreting  With,   Di- 
rections   for    61 

Batches,  Sizes  of,  Concrete  Blocks 85 

Hand  Mixing   23,  101 

Regulation  in  Proportioning 21 

Sidewalk  Work   75 

Beams,   Bending  Moment 126,  127 

Concreting  See  "Concreting  Beams." 

Continuous,   Bending  Moment 126 

Forms   See   "Forms,   Beam." 
Reinforcement.       See     "Reinforcement, 
Beam." 

167 


1G8  INDEX. 

Beams  Page 

Restrained,    Bending  Moment 126 

Span  Length,  Definition  of 123 

Tee,    Bending    Moment 127 

Bending  Moment,    See   "Beams,   Bending 
Moment." 

Beveling    Strips    in    Forms 30 

Bolt  Holes,   Filling,  Directions  for 58 

Bolt  Ties,  Placing,  Directions  for 33 

Bridges,    Specifications    for 130 

Broken   Stone,    See    "Aggregates." 
Buckets,    Depositing   Concrete   in,    Direc- 
tions for 51,     61 

Subaqueous    Concreting     With,     Direc- 
tions for   61 

Buildings,   Cement  for,   Requirements. . . .  115 

Design,    General   Assumptions 122 

Height,  Limits  for  Reinforced  Concrete  112 

Loads,    Certifícate   of  Allowable 113 

Plans,    Requirements   Respecting 112 

Specifications   for    106,  112 

Walls,   Thickness   of 113 

Working    Stresses,    Assumed 127 

Calcium   Chloride,     Amount     in     Mixing 

water,    Best    65 

Camber,  Amount  of  in  Beam  Forms 32 

Cement,   Buildings,   Kind  Required 115 

Car   Load,   Quantity  in 3 

Constancy  of  Volume,   Natural 93,  132 

Portland    93,  132 

Definition    of ,    Natural 92 

Portland    93 

Deterioration   in   Transit 3,       4 

Field  Tested 4 

Fineness   of,   Natural 92 

Portland 93,  131 

Lumpy,     Significance    of 4,  131 

Magnesia  in  Portland,  Amount  Allow- 
able      95 

Measurement,   Unit  of 1,  100 

Mili    Tested    .....       3 

Packages,   Specified 91 

Paste,    Volume   per   Barrel   of  Portland       2 

Rejected,   Remo  val  f  rom  Work 6 

Samples  for  Testing,  Selection  of. 131 

Screening  Out  Lumps ............       4 

Setting,  Time  of,  Natural 92 

Portland ......94,  132 

Shrinkage,  When  Wetted,  of  Portland.       2 

Specifications   for '   90 

Specific   Gravity   of,   Natural 92 

Portland    .. ... 93 

Storage  Houses  for,  Requisites  of. . .  .6,     91 
Storage  of,  Directions  for 5,6,7,91,  131 


INDEX.  169 

Cement  Page 

Substitutions    in    Transit 3 

Strength,    Tensile,      Requirements     for 

Natural   92 

Portland    94 

Sulphuric    Acid    in    Portland,    Amount 

Allowable    95 

Tested,  General  Use  of 3 

Tests,  Time  Allowed  for 91 

Untested,   Determinations   Required  for      5 

Volume   of  in   Bag 18,19,91,108,  146 

Volume   in   Barrel  of  Natural 2 

Portland   1 

Volume  per  Cubic  Yard  Concrete 2 

Volume  Loóse,  Increase  in 2 

Weight   of    Portland 1,151 

Cement  Bags,   Capacity  of 91,108,  146 

Number   in   Barrel 1,  2,     91 

Volume    of,     Portland 91,  108,  .146 

Weight  of,   Portland 1 

Cement  Barrel,   Capacity  of 1, "     2 

Weight  of    1,       2 

Charging,  Batch  Mixers,  Directions  for..     24 
Continuous    Mixers,    Directions    for....:  24 

Chutes,    Depositing    Concrete,    Through, 

Directions  for  51 

Cinders,  Character  and  Composition,  Re- 
quired  for  Concrete 13,  116 

Circular  Tanks,  Reinforcement,  See  "Re- 
inforcement,    Circular   Tanks." 

Clamps,   Assembling  Forms  With 27 

Cleaning   Forms,    Directions    for.. 28,  110,  143 

Columns,    Forms,    See    "Forms   Column." 
Reinforcement,      See      "Reinforcement, 
Column." 

Concrete,  Cement  per  Cubic  Yard 2 

Consistency     for     Depositing     Through 

Tremie     61 

Consistency,     Required.  50,  102,  109,  118,  146 

Cutting  for  Pipes,   etc 59 

Dry  Mixture  for  Facing,  Composition  of     69 
Handling  Rapidly  to  Place.  102,  109,  118,  147 

Loading  Tests,  Directions  for 111 

Materials,   Heating   to  Delay  Freezing, 

Directions  for   64,     65 

Materials   for,    Quality   Required   of.... 

1,  100,  106,  115,  132,  133,  142,  151 

Placing  of,  See  "Concreting." 

Proportions  Required 107,   134,  145,  152 

Quality  Required  for  Piles 82 

Retempering    Prohibited    102,118,147 

Rubble,    Placing,    Directions   for 63,  103 

Specifications  for   95 

Strength    Required    107 

Concrete,  Reinforced,  Definition  of 112 


1.70  INDEX. 


Page 
Concrete    Blocks,      Absorption,      Amount 

Permissible    160 

Age  Required  Before  Using 154 

Batches,    Size  of 85,  151 

Cement  for,   Kind  Required 151 

Compression    Strength    Required 160 

Concrete,   Proportions   Required 152 

Curing,   Period  for 88,  154 

Dimensions,   Accuracy  of 89 

Facing,  Directions  for 86 

Handling,  Provisions  for    89 

Hollow  Space  in,  Área  Permissible....  157 

Marking   for   Identification 155 

Mixing,   Directions  for  85,  153 

Mixtures  for,   Consistency  of 85,  152 

Molding,   Methods   of 84 

Molds  for,   Requirements  of 85 

Protecting    During    Curing,    Directions 

for    87 

Puddling,    Directions    for 88 

Removing  Molds,  Directions  for 86,  88 

Removing  Platens,  Directions  for 87 

Sand    for,    Kind    Required 151 

Shape,    Accuracy   of 89 

Solid,  Places  to  Be  Used 156 

Specifications   for    151 

Sprinkling,   Directions  for 87 

Stacking,   Directions   for 86,  87 

Tamping,    Directions    for 85,  86 

Testing,    Requirements   for 158 

Standard    Methods 161 

Tests  Required    160 

Transverse    Strength,    Required 160 

Walls,   Loads  on,   Permissible 156 

Concreting,   Arches,   Directions  for.... 59,  136 

Arches,    Longitudinal    Sections 59 

Transverse  Sections    59,  136 

Bars   for   Puddling,    Size   of 52 

Beams,   Directions   for 53,  105 

Stopping,   Directions  for 54,  120 

Bolt  Holes,  Directions  for  Filling 58 

Buckets,    Directions    for   Handling 51 

Buildings,   Record  of  Operations 113 

Chutes,    Directions   for  Using 51 

Columns,    Directions    for 53 

Puddling,     Directions     for 54 

Stopping,  Directions  for 56,  120 

Connections,    Directions   for 58 

Copings,    Directions    for 58 

Curbs,    Directions    for 150 

Directions    for,    General 

103,  109,  118,  134,  147,  155 

Expansión  Joints,  Directions  for.60,  105,  136 

Filling    Bolt    Holes 58 


INDEX.  171 

Concreting  Page 

Finished  Concrete,   Cutting,    Directions 

for    59 

Finishing  Surfaces,   Acid  Wash,  Direc- 
tions   for    Using 70 

Dry  Concrete,  Directions  for  Using. .  68 
Gravel  Finish,  Directions  for  Apply- 

ing    70 

Grout   Washing,    Directions   for......  69 

Methods    of    66,105 

Mortar  Facing,  Directions  for 68,  140 

Painting,    Directions    for 71 

Pebble  Finish,   Directions  for  Apply- 

ing     70 

Plaster,    Directions   for  Applying.  .70,  136 

Scrubbing,    Directions    for 69 

Spading,    Directions    for 67 

Spading     and   Troweling,     Directions 

for 67 

Tooling,    Directions   for 69 

Freezing    Weather,    Artificial    Heaters, 

Directions    for   Using 66 

Covering   the  Work,   Directions  for..  66 

Materials,  Heating,   Directions  for...  65 

Methods  of 64,   103,  110,  119,  147 

Water,    Adding    Substances    to,    Direc- 
tions   for    64 

Water,   Calcium   Chloride,    Adding,   Di- 
rections   for     65 

Water,   Salt  Adding,   Directions  for. .  65 
Frozen  Lumps,  Precautions  Against.66.  103 
Joining    New    Concrete    to    Oíd,    Direc- 
tions for 56,   103,   109,   119,  136 

Layers,   Thickness  of 52,  109,  134 

Piles,    Cast,    Directions   for 83 

Piles  in  Place,  Directions  for 82 

Pouring,   Directions   for 50,  51 

Time   of    51 

Process,    Description  of 50 

Puddling,   Definition   of 50 

Directions    for    52,54,  88 

Rubble,    Directions    for 63,  103 

Sidewalks,    Altérnate    Slabs 76 

Bases  for 75 

Time   of  After  Mixing 75 

Slabs,    Directions    for 52 

Stopping,    Directions    for 54,  121 

Stopping,  Directions  for 54,  109,  121 

Subaqueous,  Bags,   Directions  for 62 

Buckets,    Directions    for 61 

Currents,   Protection   from 63 

Directions  for    60,  102,  119 

Wash,    Detection    of 63 

Tremie,  Directions  for. 61 


172  INDEX. 

Concreting  Page 

Tamping,  Concrete  Blocks 85,     86 

Directions  f or  51,  102 

Sidewalk  Bases,   Directions  for 76 

T-Beams,    Directions    for 53 

Under    Water,    See    "Concreting    Sub- 
aqueous." 

Walls,   Stopping,   Directions  for 56 

Wetting  Finished  Work,  Directions  for 

60,  103,  110,  119 

Concrete   Mixers    (See   Mixers). 
Conduits,  Forms,   See  "Forms,  Conduit." 
Reinforcement       See      "Reinforcement, 
Conduit." 
Connections,    Concreting,   Directions   for.     58 

Copings,   Concreting,  Directions  for 58 

Curbs,   Construction,  Directions  for 150 

Currents,   Protecting     Subaqueous     Con- 
crete   f rom    63 

Drainage,  Arenes,  Provisions  for 60,  137 

Elutriation,    Method    of    for   Determining 

Cleanliness    of    Sand 10 

Expansión    Joints,    Directions    for    Mak- 

ing 60,  105,  136 

Facing  Mortar,  Applying,  Methods  of.  .68,  140 
Filling  Over  Arenes,  Directions  for... 60,  142 
Finishes,    Surface,    Classes   of ........ ....     66 

Removing    Forms    for 29 

Fireproofing,    Requirements    for 130 

Floors,   Calculation,   Directions  for 114 

Loads  Assumed  in   COmputing 123 

Forms,    Accuracy,    Necessity   of 26 

Alignment,    Checking   of 27 

Arch  Centers,  See  "Arch  Centers." 

Arch     Ring    Sections 34 

Assembling,    Clamps   and  Wedges 27 

Batter,   Anchoring   of 33 

Beam,    Camber  in 32 

Cleaning    28,  111 

Piecing    Out 30 

Removing   Directions    for 37,  121 

Removing    Time    for 36,121 

Beveling    Strips    for 30 

Bolt  Ties,   Directions   for   Placing 33 

Bracing,    Directions    for 39 

Cleaning,   Directions   for. 28,  31,  32,  111,  144 

Column,    Cleaning,    Directions    for.. 31,     32 

Openings   in   Bottom   for   Cleaning...     32 

Piecing    Out    30 

Removing   Directions    for 37,  121 

Removing,    Time   for 36,  121 

Spacing    Directions    for 31 

Squaring  Directions  for 31 

Conduit,  Removing,  Time  for 36 

Construction  of  for  Easy  Erection  and 
Removal 26 


INDEX,  173 


Forms  Page 

Coping,  Sepárate  from  Wall 58 

Curb,    Removal    of 150 

Definition   of    26 

Fabrication,    Workmanship    Required..     30 

Facing  for  Mortar  Finish 68 

Girder,   See   "Forms,   Beam." 

Jarring  by   Swinging  Buckets 51 

Joints,    Tightness    Required   of..30,  104,  110 

Loads  on,   Restriction  of 28 

Lumber,    Cleaning,   Directions   for... 30,  104 

Quality  Suitable  29 

Requisites  of   29 

Size  and  Finish 30,  104 

Woods   Suitable   for 29 

Materials  Used  for 26 

Moldings   in    ■ 30,  104 

Oiling,  Directions  for 28 

Ornament,    Construction    of 34,  135 

Removing,    Directions    for 36,  37,  121 

Removing  for  Finishing,  Directions  for    29 

Time   for 34,    36,    37,    110,  121 

Rigidity,    Inmovable    Required.  .27,  104,  111 

Runways   on    41 

Shores,  Footings  for 40 

Length    of,    Proper 39 

Location,    Directions    for 39 

Removing,    Directions    for 40 

Removing    Time    of 40,121 

Square    Ends    on 39 

Sidewalk,   Alignment  of 74,  144 

Leveling   of    74,  144 

Marking  74 

Materials    for    74 

Spacing    74 

Staking    74,  144 

Slab,   Removing,    Time  for 36,  121 

Strength,    Definition   of    Required 27 

Structural   Materials,    Storage   on   Pro- 

hibited  28 

Swelling,   Provisions   for 38 

Tightness   Required    30,  104,  110 

Wall,  Bolt  Ties,  Directions  for  Placing.     33 

Removing,    Time   for 35 

Spacers,   Directions   for  Removing  . .     32 
Wire    Ties    for,    Cutting    Projecting 

Ends     32 

Wire  Ties,  Directions  for  Placing 32 

Wedges,   Use,  Directions  for 27,     39 

Wetting,  Directions  for.28,  103,  104,  119,  144 

Wire  Ties,  Directions  for  Placing 32 

Foundations,     Sidewalk,     Preparing,     Di- 
rections   for    73 

Frost,   Sidewalks,   Protecting  from 79 

Girders,  Forms,    See   "Forms,   Beam." 

Grout  Washes  for  Finishing  Surfaces...     69 


174  INDEX. 


Page 

Joints,   Curb,  Spacing  of. 150 

Expansión,    Making,   Directions    for • 

76,    105,  136 

Making,    Methods   of.56,  76,  105,  109,  119,  136 
Sidewalk   Base,   Making  Methods   of . . .     76 

Tight    for   Forms 30,  104,  110 

Laitance,   Definition   of 63 

Lintels,  Cost,   Reinforcement  of 137 

Loads,  Assumed   in  Building  Design 123 

Reduction,    Allowed    124 

Forms,    Restriction   on 28 

Lumber,  Form,    Cleaning  Directions  for. 

30,  104 

Form,    Quality   Suitable 29 

Requisites  of   29 

Size  and  Finish   of 30 

Woods  Suitable  for 29 

Lumps   in   Cement 4,  131 

Magnesia,   Amount   in   Portland 95 

Manure,     Covering    Concrete    with,     Ob- 
jections  to    66 

Measures,   Verification   of  in   Proportion- 

ing  Concrete    19 

Measuring,    Accurracy,    Methods    of    Se- 

curing     19,     ?0 

Approved   Methods   Assumed 

17,    101,    117,  146 

Devices,    Automatic    for 20 

Measures,    Verification    of 19 

Skipping   a   Measure   Full 20 

Standard   Units  Necessary   for 18 

Mica   in  Sand,   Objections  to 8 

Mixers,   Approved   Type  Required 24 

Baten,    Charging,    Directions   for 24 

Batch,   Definition  of 23 

Type    Required 101 

Cleaning,  Necessity  of 25 

Continuous,    Charging  Directions   for..     24 

Definition     of 23 

Discharging  With  Drop,   Objections   to    25 

Erection   and   Operation 24 

Gravity,     Kinds    of 23 

Turns  Required,  Determination  of 25 

Types    of    Defined 23 

Mixing,   Concrete  Blocks,   Directions  of . .     85 
Degree  of  Required. .  .100,  109,  114,  133,  146 

Hand,  Batches,  Limiting  Size  of 23,  101 

Methods  Employed.. .  .21,  22,  101,  118,  146 

Mixing   Boards    for 22,  101,  153 

Quality  for  Reinforced  Concrete 23 

Specifications  for,  Ambiguity  in 22 

System  in  Operations 23 

When    Employed.......... 21 


INDEX.  175 

Mixing  Page 

Machine,  Turas,  Number  Required 25 

When    Employed 21,  117,  133,  146,  153 

Methods    Employed . 21 

Sidewalk  Work,   Directions   for 75,  153 

Mixing    Boards,    Construction    and    Care 

of     22,  101,  153 

Moldings    in    Forms 30,  104 

Molds,  See  Also  "Forms." 

Concrete  Block,  Kinds  of 85 

Ornament    34,  135 

Pile,   Requirements   for 82 

Mortar,  Facing,  Applying,  Methods  of.68,  140 

Facing,  Form  for 68 

Retempering,    Prohibited 102,   118,  147 

Strength    of 95,  143 

Oiling,  Forms,  Directions  for 28 

Ornaments,  Concrete,  Composition  of . . . .  135 

Molds  for   34,  135 

Painting,  Concrete,  Directions  for 71 

Pebble  Finish,  Making,  Directions  for....  70 

Piles,   Cast,  Concreting,  Directions  for...  83 

Cast,  Construction  Requirements 82 

Driving,    Directions    for 83 

Handling,    Directions   for 83 

Molding  in  Tiers,  Directions  for 83 

Molds  for,   Requirements  for 82 

Reinforcing,   Directions   for .82,  83 

Concreting  in  Place,  Directions  for.,.,  82 

Construction,  Methods  of 81 

Driving  in  Place,  Directions  for 81 

Reinforcing  in  Place,  Directions  for....  82 

Pipes,  Cutting  Concrete  for 59 

Plastering  Concrete,  Directions  for.... 71,  136 

Pointing,  Bolt  Holes,  Directions  for 58 

Proportioning,  Batches,  Size  of 21 

Correct,    Requisites   of 17 

Measures  for,  Verification  of 19 

Measuring,   Accuracy,   Methods   of  En- 

suring     19,  20 

Approved   Methods  Assured 17 

Skipping  a   Measure   Full 20 

Standard  Units  of  Measure  Necessary  18 

Measuring    Devices,    Automatic 20 

Puddling.  See  "Concreting." 

Pain,   Sidewalks,  Protecting  from 79 

"Ransomite,"   Preparing  Joints  by 5$ 

Reinforcement,  Arch,  Placing,  Directions 

for    . 138 

Assembling,    Directions   for 42,  120 

Form   of   Bars 43 

Number  of  Bars 43 

Spacing  of  Bars. 43 

Sizes  of  Bars 43 


176  INDEX. 

Reinforcement  Page 

Assorting,    Directions    for 42 

Beam,  Connecting  With  Adjoining 48 

Placíng,   Directions   for 48 

Spacing,    Directions    for 48 

Tying,    Directions    for 49 

Bending,    Directions   for 44 

Checking,    Directions    for 42 

Cleaning,    Directions    for 43 

Circular  Tanks,  Placing,  Directions  for    49 

Columns,  Design  at  Connections 46 

Placing,     Directions    for 45 

Spacing,  Directions  for 45 

Splices,   Design   of 48 

Splicing,    Directions    for 47,  120 

Tying,    Directions    for 46 

Concrete  Adhering   to 43 

Conduit,   Placing,   Directions  for 49 

Definition     of 42 

Fastening,   Directions  for 45,  109 

Oil    on 43 

Paint  on  Prohibited 43,  108 

Piles,   Placing,   Directions  for 82,     83 

Protecting  Ends,  Protection  of 44 

Purpose    of 42 

Rust     on 43,  108 

Slab,   Getting  Concrete  Under 52 

Splicing,   Directions  for 44,  47,  104,  120 

Steel,  See  "Steel,  Reinforcing." 

Storing,    Directions   for, 42 

Wall,  Placing,  Directions   for 49 

Spacing,    Directions    for 113 

Wiring,  Directions  for 45 

Retempering,   Prohibition   of 102,   118,  147 

Rocks,  Weights  of  Different 11 

Roofs,   Loads,   Assumed   in  Computing. . .  123 
Rubble  Concrete,   Placing,   Directions  for 

63,    103 

.Runways,  E'rection,   Direction   for 41 

Salt,  Amount  in  Mixing  Water,   Safe....     64 

Sand,   Artificial,   Kinds  of 8 

Clay  in,  Effect  of 7 

Cleanliness,   Determination   of 10 

Determinations   Usually  Required 8 

Grains,   Sizes  of 6,  7,  132 

Mica   in 8 

Mineral  Composition,  Determination  of 

9,     10 

Properties  Usually  Specified 8 

Quality  Required 106,  133,  151 

Shape  of  Grains,  Determination  of 9 

Shape  of  Grains,  Effect  of 7 

Size  of  Grains,   Determination   of b 

Voids  in,  Determination  of 11,  145 


INDEX.  177 

Page 
Scrubbed  Finish,  Making,  Directions  for.     69 

Shores,  Footings  for 46 

Length,    Proper 39 

Location,  Directions  for 39 

Removing,  Directions  for 40 

Time    for    40 

Square   Ends   on 39 

Sidewalks,    Bases,    Concrete,    Proportions 

of     145 

Bases,   Concreting,   Directions  for 75 

Joints  in,   Directions  for  Making 76 

Tamping,    Directions    for 76 

Templet    for    Leveling 75 

Batches,   Size  to  be  Mixed 75 

Concreting,   Altérnate   Slabs 76 

Time  of,   After  Mixing 75 

Construction,  Skill  Required 73 

Edges,  Finishing,  Directions  for 79,  148 

Forms,   Alignment,   Directions  for... 74,  144 

Leveling,    Directions    for 74,  144 

Marking,     Directions    for 74 

Materials    for 74 

Spacing,    Directions    for 74 

Staking,    Directions   for 74,  144 

Foundations,    Directions    for   Repairing    73 

Fractional   Slabs,   Objections  to .     80 

Frost,  Protecting  from,  Directions 79 

Grading  on  Sides,  Directions  for 149 

Joints,    Expansión,    Making,    Directions 

for    76 

Mixing    Concrete,    Directions    for.... 75,  153 

Placing  Concrete,   Time   for 75 

Rain,  Protecting  from,  Directions  for..     79 

Single  Coat  Work,  Directions  for 149» 

Slabs,    Thickness    of 144 

Specifications   for 142 

Sub-Base,  Compacting,  Directions  for.. 

73,  74,  144 

Materials    for 73 

Wetting,    Directions    for 74,  145 

Sun,  Protecting  from,  Directions  for...     79 
Top     Mortar,     Bonding     to     Hardened 

Base,  M*ethods  of 77 

Consistency    Required 77 

Placing,    Methods    of 77,  148 

Placing,    Time    for 78,148 

Wearing  Coat,  Marking,  Directions  for 

!79,  148 

Thickness    of 147 

Sieves,    Sizes   for   Sand  Determinations. .       9 
Sills,  Cast,  Reiníorcement  of 157 


178  INDEX. 

Page 

Slabs,   Bending  Movements 124 

Concreting,   See   "Concreting,   Slabs." 
Forms,   See  "Forms,  Slabs." 

Reinforced   in   Both   Directions 125 

Sidewalk,    Thickness    of 144 

Span   Length,    Definition   of 123 

Slag,  Kind  and  Composition  Required  for 

Concrete    13 

Spacers,   Removing,  Directions  for 32 

Spades,    Kinds  for  Finishing  Surfaces...     67 

Spading,    Directions    for 67 

Spandrel  Walls,   Thickness  of 136 

Specific  Gravity,    Cement,   Natural 92 

Cement,     Portland 93 

Rock,  Various  Kinds  of 11 

Specifications,  Bridges  130 

Buildings,    Construction    106,  112 

Cement 90 

Concrete    95 

Concrete    Blocks    151 

Definition  of  90 

Sidewalks     142 

Steel,    Reinforcing,    Bending    Test,     Re- 

quirements 99,  108,  117,  139 

Chemical  Composition   97 

Flaws  in   99,  108 

Kind  Required 97,  116,  139 

Strength,    Tensile 97,    107,   117,    139 

Test  Specimens,  Form  and  Size 98 

Variations,  Percentage  Allowed 98,  108 

Tield   Point    97 

Storage  Houses,  Cement 6 

Sulphuric  Acid,  Amount  in  Portland,  Al- 

lowable    95 

Sun,    Sidewalks,    Protecting   from 79 

Tamping.   see  "Concreting,  Tamping." 

Sidewalk  Base,  Directions  for 76 

Tee-Beams,  see  "Beams,  Tee." 

Tooling  Concrete,  Directions  for 69 

Top  Mortar,  see  "Sidewalks,  Top  Mortar." 

Tremie,  Definition  of 61 

Voids,   Determination  of 11,   14,  145 

Walls,   Building,   Thickness  of 113 

Concrete  Blocks,  Loads  on,  Reversible.   156 
Concreting,  see  "Concreting,  Walls." 
Forms,   see   "Forms,   Wall." 
Reinforcement,  see  "Reinforcement, 
Wall." 

Spandrel.  Thickness  of 136 

Wash,    Detection   of,   Subaqueous   Con- 
creting       63 


INDEX.  179 

Page 
Water,  Clean,  Necessary  for  Concrete...     15 

Impurities  Unfitting  it  for  Concrete 

15,   95,  143 

Kinds  Employed 14 

Purity,  Determination  of  Necessary 15 

Quality  Required  for  Concrete 15,     16 

Salting  to  Prevent  Freezing 64 

Waterproofing,   Arches,   Directions   for...  142 

Web  Stresses,   Computation  of 129 

Wedges,    Use,    Directions   for 27,     3£' 

Wetting    Finished     Concrete,     Directions 

for   60,  103,  110,  119 

Wetting   Forms,    Directions   for 

28,    103,    104,    119,    144 

Wire,  Kind  for  Wiring  Reinforcement 45 

Cutting  Concrete  for 59 

Wire  Ties,  Cutting  Projecting  Ends 32 

Placing,  Directions  for 32 

Rust   Spots   f rom 33 

Working  Stresses,   Buildings,  Assumed..  127 


^     OF  THE 

UNIVERSITY 

OF 


Concrete  Construction 
Methods  and  Costs 

By  HALBERT  P.  GILLETTE 

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Theory  and  Design 

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A  Treatise  for  Engineers  and  Technieal 

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Construction 

By  HOMER  A.  REÍD,  Assoc.  M.  Am.  Soc.  C.  E. 

This  is  the  most  comprehensive  book 
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nation  of  several  books  in  one,  carefully 
written  and  up-to-date.  It  has  200 
working  drawings  of  bridges,  bridge  piers 
and  culverts;  60  working  drawings  of 
sewers,  water  mains  and  reservoirs;  30 
working  drawings  each  of  retaining 
walls  and  dams;  200  working  drawings 
of  buildings  and  foundations,  including 
shops,  roundhouses,  etc. 

It  has  more  text  pages,  more  drawings 
and  more  tables  of  test  data  on  concrete 
and  reinforced  concrete  construction 
than  any  other  concrete  book  published. 
The  theory  of  reinforced  concrete  design, 
as  well  as  the  practice  of  concrete  con- 
struction, are  thoroughly  elaborated. 

Every  Engineer,  Contractor  and 
Architect  Should  Have  a  Copy, 

Sixteen-page  pamphlet  giving  table  of   contente  anf1 
sample  pages  free. 

906  pages;  715  illustrations;  70  tables; 
price  $5.00  net,  postpaid. 

This  book  and  one  domestic  subscription  to 
BNGINEERING-CONTRACTING  for  one  yeor 


Reinforced    Concrete 

A  Manual  of  Practice 

By  ERNEST  McCULLOUGH,  M.  West.  Soc.  Engrs. 

This  book  presents  the  theory 
of  the  design  of  reinforced  con- 
crete structures  in  a  manner  so 
clear  and  simple  that  it  can  not 
fail  to  be  popular.  The  subject 
is  divested  of  the  complications 
so  often  found  in  larger  treatises, 
for  the  author  has  exceptional 
skill  in  simplifying  that  which 
seems  complex. 

As  an  experienced  designer  and  builder 
of  reinforced  concrete  structures,  the  author 
discusses  not  only  the  design  but  goes  into 
the  practical  details  of  construction.  For 
example,  his  drawings  of  tools  for  shaping 
and  bending  the  reinforcing  rods,  accompanieti 
by  his  hints  on  shaping,  assembling  and  pla- 
cing  the  steel,  are  among  the  best  contribu- 
tions  to  the  literature  on  practical  concrete 
construction.  The  book  is  so  condensed, 
and  so  much  of  its  matter  is  original  that  it 
Í3  well  worth  its  price  to  every  concrete  engi- 
neer  or  contractor. 

Cloth,  5x7f  inches;  136  pages;  illustrated; 
price  $1.50  net,  poscpaid. 

This  book  and  one  domestic  subscription  to 
BNGINEERING-CONTRACTING  for  one  year  $2.50 


Engineers'  Pocketbook 

of 

Reinforced  Concrete 

By  E.  LEE  HEIDENREICH,  M.  West.  Soc.  Engrs. 

For  15  years  the  author  has  been 
engaged  in  designing  reinforced  con- 
crete structures,  and  this  " Pocketbook' ' 
is  the  outgrowth  of  his  own  needs. 

The  chapters  are  as  f ollows : 

(1)  Materials  and  Machines   Used  in   Con- 

crete Construction, 

(2)  Design  and  Construction  of  Buildi;  gs, 

(3)  Design  and  Construction  of  Bridges, 

(4)  Abutments  and  Retaining  Walls, 

(5)  Culverts,   Conduits,   Sewers,   Pipes   and 

Dams, 

(6)  Tanks,  Reservoirs,  Bins  and  Grain  Ele- 

vators, 

(7)  Chimnéys.     Miscellaneous  Data. 
There  are*  80  tables  in  this  M  Pocketbook ' ' 

which  are  alone  of  inestimable  valué  as  savers 
of  time  in  designing  reinforced  concrete  struc- 
tures. The  tables  for  proportioning  columns, 
slabs,  beams,  etc.,  are  very  complete. 

Formulas  for  designing  the  various  kinds 
of  reinforced  concrete  structures  are  deduced 
and  discussed,  and  their  application  illus- 
trated  by  examples,  thus  making  Heiden- 
reich's  "Pocketbook"  exceptionah  y  useful 
to  the  designing  engineer  who  wants  a  compact 
mass  of  information  on  the  subject  in  hand. 

Sixteen-page  pamphlet  giving  table  oí  contents  and 
sample  pages  free. 

Leather :  4}x6f  inches ;  374  pages ;  ¡llustrated ; 
price  $3.00  net,  postpaid. 

This  book  and  one  domestic  subscription  to 
ENGINEERING-CONTRACTING  for  one  year  $4.00 


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